Didn't seem to want an address to provide a digital retro thargoid hologram to go on my dashboard(s) so you should be safe to reinvest one (1) "free" ARX into that, if the offer is still available. I already have a PO box but that's not the point. I deliberately use cash to buy Steam credit for it's (apparent) anonymity.
The only reason I can think of for this move is to conjoin a physical address with activity on the forums so they can start sending out link tax invoices if the EU ever figure out how to enforce their new rules, at which point I'll happily trawl through every single post and un-link them, and probably delete the account.
The game was good enough to invest over 11,000 hours in, but not enough to be bullied.
I don't think its that nefarious (frontier also have physical products on sale and don't have the functionality to split the concepts, or they want it for fraud checks because they do the payment processing etc).
But never compromise your principles because some website asks you to. Be happy with that and they miss out, simple as that.
If you also have a itch from 11thousand hours though, another roundabout way could be to buy a new account.. new accounts since april use steam authentication apparently.. i hope you don't have to put your address in when making one of those... (worth checking though). Just on that on a recently good humble monthly elite was also on sale so i got another horizons account for peanuts including their free store credit for subscribing.. it was an old account key so so happy about that. Elite is missing from humble bundle atm so i think they finally worked it out. And completely raged at how they only received at most a few dollars for a full horizons key, lol.