Todays refusal email for CS to a BRG claim:

"Unfortunately the best price guarantee does not apply to your reservation because as the screenshot shows the price offered by hotels.com is 10 % cheaper due to the fact that they offer an additional discount on whichpoints can be earned and redeemed. Therefore I can not qualify your request for the best price guarantee."

Identical room, identical cancellation policy, identical payment at the hotel rather than on reservation. The only difference is the cheaper hotels.com rate attracts hotels.com points whereas the more expensive Accor.com rate only earns Accor points.

The refusal was quick, within the hour so at least I can cancel the Accor rate and book the cheaper hotels.com rate.