Serial Number invalid but still being used

So I successfully installed macOS Catalina on my laptop, and before doing it, I generated a new SMBios using GenSMBios, checked the serial number using Apple's Warranty Check, made sure that it was invalid, then put it in my config.plust.

After installation, I tried to create a new Apple ID, but it wouldn't let me do so because "This Mac has been used to create too many new Apple IDs"

I thought if I get an invalid serial, I would have a completely new serial number, is that not the case?

EDIT: I've tried with about 4 different serials, all were invalid in Apple's checker, but I still get the same error when trying to create an Apple ID