Sorry, but I find Orbitmic's post correct.
He stated that if you directly get a DL ticket using the reward scheme of a cc, you usually get FB miles credited. Orbitmic then continued by saying that this is not the case with the MR Amex program where you first transfer the miles to a participating FFP.
And the topic of the thread started by bertsteur is not MR Amex. He is using an RBC visa cc and he should get to get a DL reward. Although I do not know the RBC cc, it is likely that bertsteur will get FB miles credited on the DL flights.

That being said, it is true that the MR amex system allows only to transfer points to a participating FFP (the participating airlines vary across countries). That system is different from the pay-with-points system of other credit cards. However, some countries (e.g. USA) do have an Amex Plat where you can choose a pay-with-points option rather than the typical transfer option of MR.

Of course, there are also some airline-branded cc fully linked to the FFP of that airline and the points are automatically transferred to that FFP (that's the case of AF amex, but of many other cc in other countries). In some countries (e.g. USA, UK, HK), there is a vast choice of ccs that can get you free tickets. Some prefer airline-branded cards, because they do not spend that much and would never get enough points to buy a ticket in premium cabins. Some prefer pay-with-points cards because you get FFP miles on the tickets. And then the conversion ratio and flexibliity to use various airlines have to be carefully studied....