I'm fairly certain the real issue here is that Reaper does not remove TM from enemy capital ship as part of reinforcement ability. The reinforcement ability just remove TM from regular ships (which can be resisted).
The real bonus from Repaer is it's unique ability, which specifically states that "The enemy capital ship loses 15% Turn Meter whenever any ship is defeated, which can't be resisted".
Fairly certain you need a special call-out to capital ships before they are affected by abilities, I do not believe they are covered by e.g. "all enemies".