That type of toolholder is useful, with a few caveats. They will only work with fairly long pieces of tool steel, and will unfortunately quite easily turn longer pieces into a selection of short pieces if things turn to custard. The end is fairly bulky so can get in the way a bit, and this tends to cause using them with too much overhang.
There is another type of toolholder intended for shapers, it is just like the ones meant for lathes, but without the built in top rake. Because the end is slimmer it does not get in the way so much.
You can actually use the lathe type, but they are not ideal since they put the cutting edge out in front of the pivot. While this is not good from the point of view of digins and chatter, it can work, and the dovetails on my dovetail mystery, published in ME more years back than I care to remember were done this way.
Art Volz was very active on the old Yahoo shaper group, and was kind enough to send me some drawings of the authentic vice for my 6 inch Ammco. I had castings made, I really should finish machining them sometime soon!
John