So, I actually played SM and Sword again till gen 6 as it's already checked and used low power moves only on champion's Pokémon. I reconfirm that champion kukui uses 4 full restores and then in gen 8:
In sword and shield I Think they all had 1
commented Dec 11, 2020 by JackChar.
Yes, Leon uses only 1 full restore as multiple times his Pokemon were in red health but he used full restore only once.
EDIT: mistyped USM earlier, just edited it
Source: As I said, the games I replayed.
Hope I helped!