I could be misremembering, but I feel like Margaret Clark said this was the reason at Shore Leave.
She may have suggested something along those lines, but whether she was being entirely serious was unclear. She certainly had no objection when I made it clear in A Choice of Futures that the "downgrade" project was abandoned.
Besides, like I said, it just doesn't make any sense. Why would a downgrade introduced as a defense against a Romulan weapon still be in effect a century after the Romulans were last heard from?