The global release still isn't complete, they still have to release it in Europe, so they may add more games next week for the final global release. After that they'll keep adding games every month and removing others, as happened in PS Now and GP.
We know they are working on adding more games because we saw some of them rated, including PS1 emulated games like Syphon Filter 2 and 3 or PSP emulated games like Resistance Retribution or Ridge Racers 2.
There should be way less than 400 PS3 streaming games, because in addition to the native PS3 games and the thirty something PS1/PS2/PSP emulated games the "classics catalog" has many PS1, PS2, PSP, Vita and PS3 games are under its "remasters" tab of the "classics collection", which includes PS4/PS5 remasters or remakes of these games. From PSP there are the Loco Roco series, Patapon series, Wipeout Omega Collecton etc. Unlike the native PS3 games, the remasters/remakes of PS3 or Vita games like Uncharted Nathan Drake Collection or Gravity Rush Remastered are native PS4 or PS5 games so they can be downloaded and played offline.
Not sure if they are also included in that remasters folder, but I know that as exceptons a few remasters or remakes of PS1 and PS3 games are also available in Extra: Demon's Souls remake, Shadow of the Colossus remake, the Final Fantasy ones or any PS3 games included in Ubisoft+.