I agree,
and I think it's worth making a distinction if it's something informative.
In my recent Bellows gun video I made a point of calling it an Air Gun and not an Air rifle, and in future video's about Hebelpanners etc I'll also call them Airguns.
I suppose it helps if the description is accompanying an image so people can see it's a 'Long gun'
Smoothbore Air rifle to me sounds like a bit of an oxymoron.
Cheers,
Matt