Damn it! I thought I was onto something myself and was just checking to see if anyone else caught it before I posted.
Yeah, I'll need to rewatch, but I'm pretty sure every time we've heard Alchemy so far it's actually been Savitar talking. Nobody can see him, so he just makes Alchemy stand around and gesture like Shockmaster while he provides a voice-over.
Would explain the Alchemy glass scratches when Alchemy just has a laser rock - Invisible Megatron just portals into someone's room and scratches with his ridiculous stinger and nobody can see him so it looks magical.