Imagine you were building this reactivation flow. How likely would you have thought it to be that someone keeps the password to a completely unused account for 10-20 years, then suddenly misremembers it as an actually-used account and goes to reactivate it? This has probably happened on Photobucket maybe 5 times total. I don't even remember the names of any sites I signed up for and never used in 2006, let alone have interest in logging into them decades later. They could have added a check to make it clear the account is empty up front, but I can see how the person designing it thought it might be incredibly rare (and they were right).