There's nothing cryptic here. They want to have the game out in time for the holidays and would rather do that with fewer Pokemon than spend a few more months trying to get everything. There's going to be a new/cheaper Switch out at some point this year and they'll be counting on people getting it to play Sword and Shield.
"Reasons about Junici Masuda not bringing back all the Pokémon are on the 25:40 mark of the video".
> The reason is not to make players wait and to bring the game before finishing all the mons
> More details soon.
It literally says that Pokémon are not 100% ready yet, whatever that means.