Has anyone ever intentionally hidden a backdoor in publicized exploit code as a way to prevent/discourage weaponization?

I can't see how a hidden backdoor could discourage weaponization.

Yeah, if it were hidden then either people wouldn't know about and not be discouraged or they'd know about and just take it out

I've seem an exploit for Apache (IIRC) that should be executed as root and didn't worked as promised but created a new root account without password...