Well, Im no bitting expert but would assume like any single jointed snaffle it can be rather severe in the wrong hands. I used one of these bits many years ago on my ex-racer and found that he couldnt set his jaw against me as the rollers prevented it, therefore it was softer than if he had a bit in where he could take a pull and pi$$ off with me which was no fun on an open mountain
I use one on Bo and it is certainly stronger than a French link lol!
I guess two things make it more severe...
Firstly the single joint will give a harsher nutcracker action than bits with a link or nugget in them.
Secondly, the mouthpiece tends to be fairly thin which will obviously be harsher than a 'fat' one.
Have to say both my boys like it...even Trike who has absolutely no need for any brakes at all lol! Does make for lots of slobber though because of the copper