Marshadow I think they're afraid to play too much with because of Ghost/Fighting neutral pressure, but it doesn't have a good deal of distinction from Annihilape who DOES have Shadow ball (nevermind Rage Fist being prime CD move) without Shadow Claw or Punch or something. Better in ML if you roll a good one since Fighting coverage is rare but useful to back up Dragons, but not gonna make many waves since it leaves Giratina and the incoming Necrozmas as massive walls.
I wasn't expecting Marshadow to get spectral thief, but I was expecting it to actually get ghost moves.
Supposedly it still looks good in PvP, but still... no ghost moves at all??
With SendaighostGO fest being in a couple of weeks it's probably not worth hoping it's just early datamine placeholder, either.
Light trio sig moves do exist, though, and are apparently busted:
And more details on blacephalon, stak, & naganadel event are out: https://pokemongolive.com/post/dusk-mane-dawn-wings-necrozma-fusion?hl=en
That said, Annihilape DID get Shadow Ball added near-last-minute before it debuted proper; I believe until literally 2 days (January 17th) before the event dropped (the 19th) it had Primeape's Moveset minus Legacy Cross Chop, then had the same plus Shadow Ball in a dump that mostly put preview data for the new UBs we're only now getting to and some Gen 9 Legendaries. While Spectral Thief is probably something we won't see for a while if at all (like the post-Fest freebie several Mythicals get), it's proven it's never too late for Niantic to change a mined moveset, for better or worse (the latter in the case of Gogoat losing PvP Rock Slide).
As far as the Light Trio, it continues something I very much disliked about Palkia and Dialga: arbitrarily limiting it to the form they can sell now (Origin then, the Necrozma fusions in this case) at the originals' expense. Palkia and Dialga it did bother me more since they still tried to push them alongside the Origin forms in the same event, but not a fan here since you get things like Dawn Wings directly outclassing Lunala as is (to the point of getting a move buff everyone clamored for on the latter with Shadow Claw). The mons themselves are OP but still not a fan of this approach.