It sounds like Mason was actively working on The Point/Groupon for those two years, not just passively thinking about it. He quit his day job in 2006, he was enrolled as a student during the time period, he launched The Point about a year afterwards, he was in full contact with Lefkofsky during the time, and he launched Groupon a little less than a year after the decision to refocus The Point on something that could actually make money.

That's very different from dreaming up an idea and then forgetting about it for 30 years while you work on your day job.