Correct, you cannot treat a material as having a distinct edge. It is clear to me that my original text gives the impression that I treat them as having a distinct edge, but that is not intended. Anyway, like I tried to explain before, it is not relevant for my original answer if there is a distinct edge or not. What is relevant is that there is difference in propagation depending on the medium.
Yes they are behaviors of waves. My point is that exhibiting behavior of X is not evidence of being X. Take a Zebra for example. They have an interference pattern on their sides, but that clearly was not caused by a wave. Or like I said before: if I bark like a dog then I exhibit dog behavior, but that does not make me a dog. Besides, in this case photons also exhibit particle properties which waves do not, which is a clear indication that photons cannot “be” waves.
The problem here is that in the context of “particle behavior”, “particle” means solid ball or implies solidness or means something else that does not also exhibit wave behavior, while in most other cases “particle” is an object that also exhibits wave behavior. So, I will replace “particle” with “solid ball” to make a clear distinction between these two. But you must read “particle” when I write “solid ball”:
Yes, exhibiting solid ball properties is evidence of solid ball behavior but that is not evidence of being a solid ball. In this case photons also exhibit wave properties which solid balls do not, which is a clear indication that photons cannot “be” solid balls.