Is it normal for a MacBook Pro battery to regenerate itself?
There are a lot of possible explanations.  The indicator that reads battery status isn't a perfect measure.  I've seen that kind of behavior on mobile phones (uneven discharge followed by a "full charge" don't necessarily give a perfect indication of actual battery capacity).  Given that the difference you observed is around 150 mAh (out of 8755?), the difference is pretty low (less than 2%), I'd expect that to be within a margin of error for the tool.

It's also possible that the tool you're using to check capacity might be measuring total capacity by the time it took to charge the battery from a "low" state to the current state, and extrapolated max capacity from there.  That's an indirect measurement, and could be off by as much as a percent or two.

You're right, though, a LiPo battery doesn't really "improve" with age.