SOLROCK is a new species of POKéMON that is said to have fallen from space. It floats in air and moves silently. In battle, this POKéMON releases intensely bright light
It floats in air and moves silently
Therefore, Solrock is capable of flying. As a result, he can use acrobatics.
Same concept applies for Lunatone.
But to be honest, it's Game Freak logic.
It's one of those: Pikachu! Thunderbolt on your teammate, Swellow, and it will be positively charged and do more damage! moments.
Hopefully I helped - or not.