I had two pitchers on rehab assignments, and it appears that when the AAA season ended they were just left on that roster and not "forced" back to MLB roster.
It shows as "returned", but they are on the AAA roster.
I was able to sim ahead to Sept.16th and they're still on AAA roster and not required to be recalled.
Bassitt was sent on rehab assignment on September 4th, perhaps at a later date it will "force" the recall, but it doesn't appear so right now.