Philly Section Viola?

Inconclusive, but probably not - according to the statement released by the orchestra only Hsiang Hsin Ching is listed as a new violist joining the section. https://theviolinchannel.com/four-new-string-players-appointed-to-the-philadelphia-orchestra/

Are we sure he's actually done his trial yet?

Yes, I know from trusted source his second and last week of trial was at the beginning of March.