For Xerneas' "Power Creation" attack, does moving damage counters off of Xerneas to another Pokemon count as "Healing"?
No, moving damage counters off a Pokemon is not the same as healing damage (similar as to how moving damage counters onto a Pokemon is not the same as doing damage to it).
Source: BREAKthrough FAQ (2015-11-19), TPCi Rules Team (2015-11-19)

Relevant cards

Note: All applicable cards may not be listed below.
XY8_107