Of course global retaliation is affected by global conversion.
Beronath Sword was once the most powerful physical retal weapon with ele2phys conversion, before v1.1.8.2. And now it’s still used in some ele2phys retal builds of which original physical retal damage is banned (RtA Blitz for example).
This is a GT bug. In GT build calculator global conversion doesn’t affect retal damage but in game it does.