The key word is "significantly;" I would agree that by creating a line cutter, you have reduced the cross sectional area of the blade, but there is still plenty of steel left. I wonder how many blades have actually broken at the line cutter?

Doing SAR in monofilament infested waters, and working underwater, i found a line cutter really useful. In fact I took a cheap parong knife, cut off the blade squarely about an inch from the handle and ground out a line cutter in the stub, so that I had a line cutting tool that I could wield at close quarters in zero visibility waters without slicing my partners. Very specialized, but useful in that application.