aye so yeah I’ll agree with you that that is almost certainly what happened - (Cracked cylinder - ended getting a new short block)....The Subaru community has been a bastion of ignorance over the last decade. Minimal research, rejection of fact, Instagram popularity, cheap parts. These all contribute to the reason I wouldn't buy a used STI.
Not to mention just straight up unethical behavior. Search the forum and you'll see plenty of examples of "BRO, my motor just blew, what do I do?" followed by "I guess I'll remove all my mods and claim warranty action."
It's very probable someone fucked that car up and traded it in knowing full-well the issues.