Replying to Ski width accuracy

I've always been under the assumption that the widths given on a ski are taken from the base of the ski so you understand the total footprint you're getting. However after just recieving my '13 icelantics and the correct widths they gave are taken from the topsheet. I don't mind because 105 was the skinniest stick on my radar and the actual narrowest point on is 112mm,, but it did force me to buy another set of brakes for my new bindings which was annoying. Is this normal or is icelantic off with their measurements? Very misleading