Perhaps, as they may not get bonuses to repair from veterancy. A vet 3 engi squad getting vet 0 conscripts may very well repair slower. But the fact that there is such a thing as conscript repair, I really am unsure exactly how repair works with merging conscripts. That's actually an interesting question.
But anyway, the veterancy is squad based, yeah, but when bonuses are applied from that squad onto the entities, those effects are retained by the entities when they change to a new squad.
I didnt ask the questions in literal terms, they were meant to be rhetorical.
a vet 3 engy squad with cons in it will repair just as fast as one without cons in it because its a squad based bonus.
a vet 3 con merging into an engineer will lose its terminator received accuracy bonuses gained from its conscript veterancy, and become an engineer veterancy wise. They reset right back to vet 0, or whatever-vet-of-the-squad-whatever-they-merged into.
The only thing the squad retains whem merging and crewing is its unique entity identity. aka ebps. its seriously not that intricate.
You can simply test it for yourself if you still dont believe me.