As "more or less confirmed" as we can ask for with Khu, but no official confirmation. The sensible bet is that all trio paradoxes are obtainable in-game without raids, as otherwise they wouldn't be in any dex and would effectively be mythicals if they are only obtainable through events.
Edit: then again:
https://x.com/hsinhsung9487/status/1721653194198008257?s=20
View attachment 568957
I interpreted "event" to mean a story event, but I suppose it's possible TPC really just mean a raid event, which for the aforementioned reasons I would consider to be a dumb decision. But then again, Zoroark in BW was basically event exclusive...
For the other legends the best we have to go on seems to be the 25 sidequests datamined from Teal Mask, but if those correspond to legendary encounters then it doesn't account for all of them, so some may still be HOME-transfer only (or you get choice of one out of X in some sidequests, etc), assuming of course that Khu's tweet indeed implies every single box legend and sub-legend makes it in and he didn't overlook any sublegends that didn't make the cut. (And who knows about the remaining mythicals, since they didn't all make it in SwSh).