Very interesting. I didn't think to check the X570 motherboards' EEPROMs.I've noticed there are a few X570 with 16Mb eeprom. If the 4xx series boards require 32Mb surely all x570 should have that?
Indeed you're right. The motherboard that I've been eyeing up only has 16MB (128Mb) EEPROM:
https://www.gigabyte.com/Motherboard/X570-I-AORUS-PRO-WIFI-rev-10/sp#sp1 x 128 Mbit flash