It certainly looks like a hybrid.
About ten years ago, I saw a M. duwei in Walter Hellinx's collection, which carried my field number WTH 460. This certainly was a hybrid. Walter told me that it was grown from seeds which I had given to the German Mammillaria Society and which had appeared in their seed list. In those old days, I did not completely exclude bumble bees from entering my greenhouse (nowadays I do) and I assume that it was not only I, but also bumble bees who had pollinated my duweis (which I had grown from habitat seed, i.e. OK).
To me, it was clear that M. duwei can be hybridized. I threw away my own (hybrid) seedlings, except for those seedlings which looked like the real duwei (yet, I don't use these plants for pollinations). Among those duwei seedlings there was even one which produced reddish flowers. I would have liked to see that one grow up, but sadly it died soon after the first flowering.
Another mammillaria where I have noticed hybridization in my collection is M. swinglei WTH 681 (grown from habitat seed). The plants which I grew from their seeds sometimes had reddish flowers, which was not what it should be. I wrote to the owner of the German seed list that he should throw those seeds away, which he did only a year later (current WTH 681 seeds in the AfM seed list are OK, though).
Nowadays, the doors and self-opening windows in my greenhouses are covered with a net, such that bees cannot enter anymore.
So, to all who pollinate their plants: exclude bees!