You have some points. Regardless if winged dragons are more common, your claim that all dragons have wings, even though I already pointed out Spike _didn't have them in previous MLP generations/canons._ There are some other examples out there, (Disney's "Reluctant Dragon" comes to mind.) So dragons being portrayed without wings isn't completely unheard of in Western media as you claim.
So as I said it's understandable why some bronies wouldn't see it coming, or why some find it jarring for Spike to suddenly grow them despite winged dragons being common in the FiM canon.
Still, as I said I don't feel strongly about it either way, I am curious to see how it goes. (Though, avoiding more spoilers, to avoid making any pre-judgements.)