He had 65 warning points. That muted him (above 60)
Reducing him to 55 allows him to post everywhere again, and he does.
1 warning point is automatically removed every day.
Let's say the case takes 6 days. He'll be down to 49 at the end.
Even if you add back the 10 points, he'll be at 59 - not muted.
So he can post now, and once the case is done.
So yes, this does effectively negate the moderator actions of the past month.