They didn't, though? The multiracial founding fathers thing was a side effect of what one assumes is pretty normal prompt engineering. Marketing departments everywhere have rules and standards designed to prevent racial discrimination, and this looks like "make sure we have a reasonable mix of ethnicities in our artwork" in practice. That's surely "bias", like I said, but it's not deliberate political ideology. No one said[1] "we need to retcon the racial makeup of 18th century America", it was just a mistake.

[1] Or if they did, it's surely not attested. I invite links if you have them.