They mean is that they are much harder to acquire. Their goal is to become an independent public company.
But they are not independent though, they will be owned by Wall Street should they go public.
Instead they remain in the private markets for a long time and sell secondary shares, just like what Stripe is doing.
I hope they never go public for the reason that Wall Street would own them.
That depends on how much equity they issue as public stock. (And stock classes and voting rights, but you get the idea.)