The BMI block to block times are the same - I agree. The difference is that you have some leeway as to when you arrive at the gate Provided you getto the gate on time - no problem. At BA conformance adds an extra 15 minutes to waiting times ( at the very least) and if you don't make conformance you get bumped regardless.
Interesting that BA will waive conformance for some pax - it will make the rest of us feel even more disadvantaged.
I have no hatred of BA but a loathing of petty bureaucracy that is ruining what was once a great company.