It's unfortunate they can't just explain the real reason they don't want to generate the image:

"Unfortunately I'm not able to generate images that might cause bad PR for Alphabet(tm) or subsidiaries. Is there anything else I can generate for you?"

The rejection message doesn’t seem to be accurate. I tried “happy person” as a prompt in AI Studio and it generated a happy human without any complaints.

It’s possible that they relaxed the safety filtering to allow humans but forgot to update the error message.