That theory would predict that people on the same age, but with bigger vocabulary (or expertise in a particular domain) take more time to pick words (or make decisions in that domain) which is the opposite of what seems to happen in everyday life.
I find myself struggling more to pull a specific word out of memory than I did when I was younger. I have chalked that up to the amount of information held in my memory, and that my search algorithm isn't very efficient. Sometimes the answers to a question take days to bubble up out of my memory banks.