The word "fantasy" as applied to muzzleloaders is a continuation of the same word as applied to swords, etc. - they are pieces that have no historical precedent but are products of the makers' imagination. The only real difference is that fantasy swords, etc., are usually made within the context of an explicitly imagined universe, such as those invented by Tolkien or Howard, whereas fantasy flintlocks are not.*
The exact delineation between a fantasy piece and a recreation of a historical example is pretty murky and a legitimate discussion, but the basic concept is pretty simple. I'm not sure why so many people seem to have trouble with it, unless they simply aren't aware of a rather significant literary and cultural phenomenon of the last century and a half....
In sum, no, those are not fantasy rifles, because the word "fantasy" in the context of modern-made weapons (and many other things, as a matter of fact) means something quite different from how the OP is using it. This is not a word that is confined to our own little circle, but is an extrapolation of a concept recognized world-wide, so I don't think that there is room for debate on the matter.
On a more general note, there is absolutely nothing wrong with making a fantasy/contemporary longrifle. I think it is a sign of that the art and mystery of longrifle-making is healthy and alive, as a matter of fact. The problem is when a fantasy rifle is (as they often are) labelled as a historical piece. It would help things a great deal if people would label their creations in a straightforward way so that they can be judged fairly - if you are making a recreation or interpretation of a historical piece, expect it to be judged as such. If you are making modern fantasy piece, expect it to be judged on its artistic merits and as a continuation or commentary on tradition (all art of any genre is made within the context of earlier art, this is not unique to longrifles!) This allows for both good and bad examples of both genres. Personally, I think that making a good fantasy rifle is every bit as difficult as making a good historical piece, and requires an intimate knowledge of historical examples from which to build on.
*To answer the obvious objection: No, just because a story is theoretically set in the past does not preclude it being fantasy. Historically-based fantasy literature was actually pretty normal for most of western history - see the King Arthur legend for perhaps the most important example- and setting stories in alternative universes only became standard after Tolkien published The Lord of the Rings in the 1950s, I believe. Even the Conan stories were set on Earth in an imagined earlier eon. Modern Asian fantasy is often set in a more or less specific historical period - the Judge Dee movies on Netflix are an easily accessible and obvious example, 14 Blades is perhaps more subtle.)
