Technically his rehab is over. What's happening now is the time at AAA he was supposed to get after his removal from the 40, and it wasn't necessarily meant to be short (he was DFAed on June 8 last year so they were probably thinking August, if at all). Not sure the 23 games and .599 OPS last year even count.
And unfortunately sometimes a player needs a half-season or even full season to really find his groove again after surgery and a big injury. Plus in Kingery's case the groove was already gone, dating back to late 2019. And technically he never got enough time in AAA when he was a rookie!
I hope he forces his way back onto the 40 but many miles to go.