I'm so intrigued by you having an account since 2011 and this is only your 5th comment.

They may have another account they use when not speaking as a googler

Nope, this is my only account (assuming you can trust anything I say). I signed up a while back when I was founding a startup company (because of course every founder needs to be on HN), but then stopped coming here after the startup disintegrated. I've started coming back after I got bored going to r/programming during long compiles.

What's the case for not allowing these accounts? What do people reply internally?

Don't know, but probably there's some arbitrary legal complications associated to personal accounts so their lawyers simply decided to put those accounts into the "enterprise" category to avoid all the messes and now we're seeing collateral damages from this short-sighted decision.

Google apps for your domain is handled by the GSuite team. All their accounts have various extra requirements, like legal checks, not randomly adding features without consulting the admin, having different sets of servers for some services, having different treatment of private data (since the domain admin must be able to have some control over it) etc.

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.

That makes it even more entertaining that they end up railing against the same poor google product policies. Does nobody ever collar a product manager in the hallway?

Said managers are very good at saying "I'm afraid it isn't a priority for our team at the moment".