I don't think the OP is lying. Their account was probably locked because they missed a payment. I do think this is a misunderstanding of what's happening.

They're paying for iCloud with their Apple Card. If that payment fails, the account can be locked.

So it's not "Missing a payment on the Apple Card locks your account" it might be "Missing an iCloud Payment locks your account."

They also say the iCloud payment wasn't past due. I wouldn't be surprised if this was some weird edge case or bug that caused the account to be locked.