What the hell, I just tried this and it turns out to be true. Sometimes I think I should go work for google for a year just so I could rage internally about this sort of shit. I too have a GAFYD account I've been paying for since 2009.
People do rage internally about this. Unsurprisingly, a lot of current Google employees were early adopters of new Google features.
Some product teams within Google don't like all the extra overhead, paperwork, and complexity that adds, so instead they just block all enterprise accounts.
They refused to allow me to pay them more, and refused to allow me to transfer my purchases to another account I verifiably own so I could then pay them more.
I know legacy GAFYD accounts don't matter to Google, and I don't expect them to, but it'd be nice to be able to transfer my stuff out. I know we like to point out who Google's real customers are, but after a decade-and-a-half I've actually paid them real money for things, and shockingly would like to continue doing so.