Terminology is a funny thing.

Every art studio that I worked in has mat knives & mat cutters.
Mat cutters are for cutting photo/frame mats as you described.
Did I mention that I hate cutting mats?
The only thing worse than cutting mats is cutting double mats with a 1/8" difference in size. Any little mistake shows.
Anyway, you are correct about the mat knife being a snap off utility knife/blade.
Again it is called what it is called.
Used in my world for cutting everything other than beveled edge photo/frame mat boards.
We mount prints on mat board and either cut them flush to the edge of the print or leave a border around them. Just cutting straight edges. Not beveled edge photo mats.
The last time I counted we had 12 different kinds of board in the studio, from 1/2" thick foamcore to 2 ply railroad board (otherwise known as posterboard or oaktag) with all the stops in between.
It isn't uncommon to mount a houndred hp prints (plots) on a hundred sheets of 3/16" foam core board and trim all four sides.
400 cuts for one meeting. A really big meeting like the one we're working on for the last week will be a couple hundred boards from 15x20" all the way up to 48x96"
Sometimes it isn't foam core board but double black illustration board.
Or 14 ply white.
My point is, that in any art studio that I've ever worked in it is referred to as a mat knife.
And yes you are correct, it is a snap off utility blade...but we call it a mat knife

I only stress the point in case you walk into an ad agency studio and need to cut something...wouldn't want you to confuse the poor artists
