It is not really a benefit though, more like a loophole, that BA has now closed.

As a datapoint I noticed that my points earn at the weekend credited as J instead of the usual F, and the suggested points earn in a booking I made some time ago is now at the original booking rate rather than the upgraded cabin rate. As it happens my travel agent is now on their third attempt to book my regular routing and apply a GUF1. Fingers crossed things haven't changed on that front.