That would be innocuous, except that it's a way to send a very small UDP packet to a DNS server and generate a very large UDP packet in response. Since UDP is easily spoofed, attackers can use ANY to amplify DDOS attacks. It's painfully effective in practice.
So far as I can tell, no normal part of the DNS process ever relies on ANY queries; there isn't a thing your browser or OS or SSH or access point does that ever calls for a "give me every regard regardless of its type" query.
From TFA:
As there is no good reason for applications to ever issue an ANY query this document codifies how an authoritative server can reject such queries.
This raised my eyebrow, because the standard argument DNSSEC apologists have for that (terrible) protocol's in-built DDOS reflection capability is that DNS also inescapably has that property due to ANY.
I've tried arguing that ANY is pointless and filter-able, to little avail. It's good to see Gudmundsson, an unimpeachable IETF authority, saying the same thing: ANY queries are bad, and not a fundamental part of the DNS service model.