Dropping anchor can provide stability by keeping the bow (pointy end) facing into the waves. I don't know how deep it was where they were, but you are supposed to depoloy at LEAST three times the anchor line as the depth (i.e. 150 feet of line if you are in 50 feet of water). That is a minimum, or your anchor is going to pull free of the bottom each time the waves push the boat up.

Having said that, it would not be my first choice in those conditions. I would do it only if there were no other options, such as if the engine died.