I don't think the issue is making employees wealthy or not: It's 10 year old RSUs, so most of them are owned by former employees. But consider the size: If the tax bill is 3.5B, the full size of the grants we are talking about here is over 10B! last valuations in the press are at something like 60b. So 1 in 6 shares in the secondary market? Might as well be an actual IPO.
Without 2022 going the way it did, I'd have expected that there would have been yet another regular round, where the investors ate enough common stock for current and former employees to vest the RSUs. That, or maybe the company really IPOs, which clears out all the comp problems. But Stripe finds it very valuable to keep the company closed, so instead of IPOing when everyone else does, they delayed too much.
So there's no real need for not wanting people to get rich here: It's just a very uncomfortable amount of stock to have to turn into liquidity either way.