You missed the second part: "But that was in the days of IPOs, now the investors prefer to keep the rise in equity to themselves. So you chances of winning the lottery are much less."
Hence the "it worked for him then, but probably wouldn't work for anyone else, now"
Instead of selling your shares right after the IPO, couldn't you trade options on those shares in a way that closely simulates selling the underlying equity, and stay within the agreement?
On the options - I'm honestly not sure. I don't think it's barred by contract (since that's about managing actually control and share movement), but I don't know what options trading looks like for newly-IPO'd stocks.