It’s not a sure thing, but likely, that you and the other party have now been associated in some database, or will be. Creditors/debt collectors are the most likely to make tenuous associations, the least likely to care, and the law doesn’t force them to be accurate. It would be a good idea to monitor your credit report periodically (it always is), and this connection might show up years later, when you’ve forgotten the details.
Not overly worried, no credit cards, no car loans, no mortgage. I do a ritual check on the big 3 credit companies once a year and the results are pretty boring.
Email address account names can be case sensitive, but to reduce confusion, nearly all email providers make their account names case-insensitive, so JSmith and jsmith are the same account.
Gmail goes even further, and does things like ignoring periods (j.smith and jsmith are the same account) or anything after a plus sign (jsmith+1 is jsmith).