I reserved a stay at the Renaissance Arc de Triomphe in Paris during a promotion. It was advertised that bookings made during that period would get 5,000 bonus points. The bonus didn't appear, so I asked why. I was told that it was because I had reserved at "Stay for breakfast" rate, which didn't get the bonus, but if I had paid the lower price for "Discount rate", I would have got the bonus! Quite apart from the puzzling logic of giving a bigger reward to those who pay less, there was no warning of this condition when I made the reservation.
Often the "bonus points" offers are found in the "Promotion Central" area of the Marriott website and are different than other promotional offers (e.g. Breakfast, Shopping package, etc.). I know in my experience that when I have booked a "bonus points" offer I was also shown other rates at the same time. I have seen "bonus points" rates both higher and lower than other rates being offered at time of reservation. I am not sure if this will be helpful, but wanted to share my experience.