The average user doesn't have the level of visibility into the system to know that the middlebox is the one causing the problem. Instead whatever changed last gets the blame, regardless of what's actually at fault. So if a user's existing applications set the spin bit "correctly" and a new application does not, the new application will be judged as buggy, not the middlebox which has been working fine until now.
All they can do is corrupt or block the packet, which looks to the end user like high packet loss on random connections... earning that router type a reputation for being very slow and pushing it out of he market.