I don't think 'return fire' should be that quick, return fire should be activated after attacker go back to cover

Unit attacks → Attacker freezes and takes damage → Attack ends, the unit goes into cover
+

Overwatch is triggered after a moment / meter of enemy movement. He was ready for action, but shot with a delay, and it looks legal.

For RF you need something like that, but it’s better to turn off freezing.