Yes, but why couldn't they have assigned .mdns for that instead? Or even better given it it's own .arpa domain? E.G. .mdns(.arpa) rather than the .local TLD? ( https://en.wikipedia.org/wiki/.arpa )
Because .local looks nice and is a better name/explainer for what mDNS does than the standard name or the old brand name? Because the old brand was already using .local even if Apple Devices were somewhat a minority at the time?
At this point a lot of TLD changes are going to step on someone's project or home/business/private network. I think .local is a good name for mDNS. I appreciate why you maybe aren't happy with it, but don't share your concern.
Those are both reasons that .local should be static DNS on the _network_ like localhost is a standard name for the loopback address(es).
There's no reason .mdns or .mdns.arpa couldn't have just been added to the default domains search list (the list of suffixes tried for non FQDN searches); which given it ISN'T a nice human obvious word to append wouldn't have conflicted with anyone who'd already had a .local at the time, and anyone else in the future who thinks an obvious phrase like .local would not be in use by some other resolver system.
