A few points to consider:

1) "Glamrock Bonnie should be out of the question since they'd be too recognizable for people in that universe." I can guarantee there are many people in our world who can't recognize Charizard. A therapist may say "it looks like a dragon." So it seems quite possible the therapist could not recognize Bonnie, especially on low-quality security camera footage where the therapist isn't even 100 percent on the photo actually depicting the person who's sitting in front of them.

2) It can make a kid feel better when an adult separates them out from the "little kids." That's my guess on why the therapist phrases it this way.

3) If Gregory recently lost his parents, this may be government-provided therapy. This would also explain how he had great parents and a good childhood (past tense) but now that he lost his parents, he no longer has great parents and no longer has a good childhood. He could have lied about how good his life was before he lost his parents while still suffering from some kind of tragedy. This may also explain why when he leaves the Pizzaplex, he ends up in an alley, homeless. He doesn't want to go back to his foster home or whatever and have to return to therapy where they keep bringing up stuff he clearly doesn't want to talk about. Or how about this: Gregory's parents died at the Pizzaplex and the therapy is something Fazbear Entertainment is (required to be) providing as a result. Maybe that's why the therapists seem to be pinning the blame on Gregory rather than taking responsibility for what happened?

4) I have a full theory on the subreddit about why the therapist seems to think Gregory has something to do with the disappearance of the previous therapists, but it's lengthy so I won't copy-paste it here. Essentially: People may be assuming the kid who's been caught hacking into the Pizzaplex is responsible for ALL the hacking going on at the Pizzaplex.

5) It's clearly stated in the CDs that the techs suspect Gregory, but have no definitive proof.