I know the change was made to Jhoira so that reinforcing her also triggered her draw ability, however this changes also seems to have been applied to Mishra’s Self-Replicator; either intentionally or not.
This means Mishra’s enters the field as an 8/8, and any time you cast it again, it gains 8/8 rather than 4/4.
It’s a bug in the sense that his first play reinforces itself. He’s not on the field for that to trigger his effect. Its retroactively triggering the effect after the fact.
Any subsequent castings of itself should work this way but not the first.