I'm not exactly sure what you're saying here. Could you clarify this?
Carla is an informant, but I don't think she's a synth. She's on that list, as most of the wandering vendors are. I think they're just paid informants though, and not actually synth replacements. I've never killed any of them to find out if they drop the synth component, so I'm not sure.
He could be a freed synth who had his memory wiped too. I've always assumed that it implied that he was a synth replacement and I've never considered the idea of him being a freed synth. That's a good question. It would be cool to see this expanded upon in some future DLC.
I don't think Glory is actually a human. I think that was just an oversight on the part of the developers. Roger Warwick is a synth as well and doesn't drop a synth component. Again, I think that was just an oversight. In both cases, these are the only synths within a group of humans. I think it's reasonable to assume that someone simply forgot to add the synth components to their inventory.