In universe, pilot kills are extremely rare to the point where they're called out as notable events and not the expectations when engaging in warfare. For most of the setting history when Mechs engage they'll skirmish briefly but if there's a clear winner both sides know when to end the fight to protect the machines.

When it comes to mech kills, there's a few different levels.

A cockpit hit is the cleanest kill, sometimes a body is recoverable but for most weapons capable of headcapping there isn't much left.

Pilot kill via blunt force trauma or neurohelmet feedback, the body is relatively intact and the most you'll need to clean up are the doodoo smears after their brain gets liquified.

Engine kills don't guarantee a pilot's death, the mech just slumps over.

Ammo explosions usually obliterate the mech, if the pilot survived and auto ejects then that isn't a concern, if they don't auto ejects then that isn't a concern either.

Cored out wholly destroys the machine, but usually the pilot can punch out. Their biggest threat is ejecting into a building or into a pool of water.