I saw this coming at some point, and when even actual Stall Players are noting the uncompetitive arguments against one of Stall's greatest assets, it says something about this mon's effect on the metagame.
Dugtrio's boost to attack and the metagame slowing down just a tad compared to last gen does it a lot of favors as a trapper. As of right now, the only OU relevant mons that outrun Dugtrio without an item or boost as Tapu Koko, both Greninjas, and Pheromosa, and I think it fair to say these aren't what come to mind when Defensive teams prepare for Stallbreakers in particular. Dugtrio's Base 100 Attack doesn't seem like much, but STAB Earthquake off of that is enough for its role, in which unlike other offensive mons Dugtrio isn't dealing with prediction or switches to bulky walls. It's not cracking down entire cores, but it's enough to deal with offensive threats after at most a bit of wear and tear, which is the name of the game for Stall teams.
With the increasing number of (viable) threats in OU, the load on each individual team slot only gets greater and greater. Thus, the cost of losing a mon in (optimistically) a 1-v-1 to Duggy becomes a larger hit to the team's performance as well. With the increase in ATK from "needs to hit SE" to "actually kind of passable with high BP coverage", the list of mons it can be considered a solution to got larger, while they have more weight on their backs in the metagame at large to value their preservation. It's also a Catch-22 to play against Dugtrio: the less important a mon is to the opposing team match up, the less ideal a choice it can be to bring them in for momentum reasons or risk of offering set up bait, and vice versa. Since Dugtrio doesn't allow switch counterplay, there's not really a risk to bringing it in if the chance is created, meanwhile you have to keep your most valuable mons vs the Duggy team off the field because of it, so the ones who in theory do the most work can end up doing the least work in practice, whether from hesitation or from getting picked off by Dugtrio before their work is put in.
I admittedly can't add much that hasn't already be said, but I do agree with the decision to start with Dugtrio. Its stats aren't spectacular in their own right, but in the context of being a near uninhibited trapper, they're well above the numbers they need to be at. It says a lot to me that Dugtrio Stall has turned Hoopa-U, a mon that was S-Ranked (even ignoring the ban) in ORAS OU for its ability to eat defensive cores/teams alive, into a mon that is at best hanging around a very crowded A- tier and just generally doesn't see much discussion anymore, indicating it's not likely to move up or down. Just one example, but whether Arena Trap or the mon itself, it shows just how important Dugtrio is to Stall as a playstyle to prepare as and against.
Dugtrio's boost to attack and the metagame slowing down just a tad compared to last gen does it a lot of favors as a trapper. As of right now, the only OU relevant mons that outrun Dugtrio without an item or boost as Tapu Koko, both Greninjas, and Pheromosa, and I think it fair to say these aren't what come to mind when Defensive teams prepare for Stallbreakers in particular. Dugtrio's Base 100 Attack doesn't seem like much, but STAB Earthquake off of that is enough for its role, in which unlike other offensive mons Dugtrio isn't dealing with prediction or switches to bulky walls. It's not cracking down entire cores, but it's enough to deal with offensive threats after at most a bit of wear and tear, which is the name of the game for Stall teams.
With the increasing number of (viable) threats in OU, the load on each individual team slot only gets greater and greater. Thus, the cost of losing a mon in (optimistically) a 1-v-1 to Duggy becomes a larger hit to the team's performance as well. With the increase in ATK from "needs to hit SE" to "actually kind of passable with high BP coverage", the list of mons it can be considered a solution to got larger, while they have more weight on their backs in the metagame at large to value their preservation. It's also a Catch-22 to play against Dugtrio: the less important a mon is to the opposing team match up, the less ideal a choice it can be to bring them in for momentum reasons or risk of offering set up bait, and vice versa. Since Dugtrio doesn't allow switch counterplay, there's not really a risk to bringing it in if the chance is created, meanwhile you have to keep your most valuable mons vs the Duggy team off the field because of it, so the ones who in theory do the most work can end up doing the least work in practice, whether from hesitation or from getting picked off by Dugtrio before their work is put in.
I admittedly can't add much that hasn't already be said, but I do agree with the decision to start with Dugtrio. Its stats aren't spectacular in their own right, but in the context of being a near uninhibited trapper, they're well above the numbers they need to be at. It says a lot to me that Dugtrio Stall has turned Hoopa-U, a mon that was S-Ranked (even ignoring the ban) in ORAS OU for its ability to eat defensive cores/teams alive, into a mon that is at best hanging around a very crowded A- tier and just generally doesn't see much discussion anymore, indicating it's not likely to move up or down. Just one example, but whether Arena Trap or the mon itself, it shows just how important Dugtrio is to Stall as a playstyle to prepare as and against.