412M domains registered worldwide

700 changes per second implies 15% of all domains are changing daily, which is almost certainly not the case.

It's well possible that some people update DNS records for their own domain every minute.

I can see 15% changing daily. There's all sorts of stuff being done with dkim and other anti-spam technologies that require a txt or cname or whatever change in DNS. Companies are always whitelisting vendors and mass mailers to send as them, validating domain ownership, adding new sub-domains, changing things for Exchange/365/Google/AI stuff, changing things due to a security audit, etc.

I imagine a renewal is a change event to, at least change the expiry, and renewals are constantly happening.

It's probably more like most domains barely change at all but some of them change a lot.