I'm not sure how effective the clotting agents are. I was watching a cooking show and one of the chefs chopped off the tip of her finger. They put a powder on it, presumably a clotting agent, and it still squirted. Eventually they resorted to bandaging and the show continued.

Perhaps it was not a clotting agent (or a GOOD clotting agent), or perhaps fingertips don't have enough surface area for it to work well.

Of course, just because it was on TV, even a 'reality' show, does not mean it was a reliable source of information...