GPT-4o was considered harmful, because it imitated human connection too much, not because it was so "smart" or capable.
It was for sure a deliberate decision to make LLMs seem less like a human companion and more like an obedient servant in newer releases.
4o was considered harmful because it never disagreed with the user, pushing them into depths of AI psychosis that lead to suicides and murders.
Interesting. The reasoning models were super weird and robotic. They toned that down a bit in GPT-5.x, especially the later ones.
I always assumed the strange style was an artefact of the RLVR.