This is pretty common and something that bit us last year - enterprise Outlook 365 (or some extension? idk it was def only O365 though) added some security features that would make a HEAD request to any links contained in an email. This messed up our (admittedly antiquated) process for activating users and resetting passwords as it consumed the one-time code our systems generated for them, as you mentioned. Because the app that handled this was old and in the process of replacement we didn't want to invest too much time in rewriting it all, so a quick and easy fix was to have a handler specifically for HEAD requests to those activation and reset resources. The link protection started issuing GET requests a little while after, so we ended up having to add an extra confirmation step so the user had to click something after the link was followed.

To be honest the original process we had maybe wasn't 100% perfect - users can double click links for example, and would see a message that the link had "expired". So from a UX perspective we maybe should've had the extra confirmation step before activation/reset to begin with. But I'm in two minds over email providers following all the links in your emails, it feels a bit creepy