You're getting the benefit that AWS isn't just a registrar they're... AWS. Their processes around accounts and support and such are all designed around much higher value and higher impact accounts (many entire businesses would go away if all their compute + storage were suspended). Low margin domain registrations isn't really their business, so they're not trying to cut security/support to make it viable. From $4k/yr accounts to $450k/yr accounts, I've never had an issue getting in touch with support and having someone empowered to resolve my issues.
That said, I'm assuming from "enterprise-y" that this isn't anything that would be remotely near violating their AUP. I haven't heard of much real enforcement outside of people who were very blatantly malicious actors, but I'm sure if I don't mention it someone will come along and point out one of the newsworthy account suspensions that have happened.
It's everything you need from a registrar & DNS provider with nothing you don't: a thoughtful interface that is responsive even with a large volume of domains, no up-sells, first-class API capabilities (which is great for volume/bulk operations), and the pricing is solid/reasonably low-margin with no gimmicks, no front-running.
Only thing to note is that, at least last I looked, Amazon isn't actually the registrar -- it's some kind of 'affiliate' setup with a 3rd party, but AFAICT it's essentially Amazon.