Trouble understanding how a custom Signet works in Bitcoincore.

Hello, I have set up a custom Signet node, with my own challenge.

I thought that to issue a correct block for Signet, one would need to sign it with the proper miner and that would not be possible to use the `generatetoaddress` API for issuing blocks as it's done in regtest.

I was wrong, at least with bitcoincore 0.21.1, and I don't get why I can still emit valid blocks with just the Proof Of Work.

Could anyone kindly take a sec to explain why this API still works, or point me to the codebase consensus part for Signet, maybe?

Thank you very much.