I am not sure how can they tell if those AMEX MR are sign-up bonus or not. They are MR points, and show up the same when it come in to your account. I think this T&C might be referring to Aeroplan Credit Card Sign-up bonus like CIBC (or future TD) Aerogold and AMEX AeroplanPlus.
On my transactions, MR points are not credited towards distinction.