I accidentally did the same thing, because the Free Trial PS5 version was live before the Digital Upgrade was. It looks like the only difference is that the digital upgrade will only upgrade an existing user account, whereas the Free Trial version has all the extra stuff when you first run it that could set up a new account for the Free Trial; when I ran the Free Trial client, it walked me through all the "this is what you'll need to create a free trial account" and then gave me an option for "I already have an account". Clicked that, got the usual login screen instead of the set-up-a-new-account stuff, and everything was as normal from there.

(Except very, very zippy and crisp compared to previously.)