Do people need your approval to register to Hive?

No they don't. This is part of a pre-designed response by the onboarding project I am part of.

did you tell him using AI and not disclosing it is considered abuse on Hive?

The very first thing they are thought and made to properly understand is Only original content is allowed. No copy pasting, no AI. Many of the newbies follow that rule. One or two might decide to play naive.

Will still do my work to call him to order again.