I assumed it was a shitpost, instead it is a real tweet. What a time to be alive.
Jokes aside the only real reason I can fathom for the collectibles company to call their mother is because they had used it as the contact number in the registry. I would be surprised if this was some kind of intimidation tactic instead of just miscommunication - in the sense they probably just wanted to legally intimidate the itch's owner not their immediate family. They are not 2K/s.
Can I just point out this was standard practice for debt collectors like 15 years ago? Seriously they'd try to call your job, your family, neighbors and if they could, even friends to harass you to collect on the debt they bought rights to collect.