No law, rule, or custom was broken by the buyer, so this is not fraud on his side. The seller on the other hand has lied to customers - they claimed it was 16T

No law, rule, or custom was broken by the buyer, so this is not fraud on his side. The seller on the other hand has lied to customers - they claimed it was 16TB drive and it was not. This is 100% definition of the fraud, and ideally seller would be penalized for that.