I've no idea if they feel they need this or not. But I do know that if you want to buy a significant chunk of JS (which is the context of this) then you'll need to have a lot of money to do so.
They typical reason hedge funds set minimums (aside from regulatory restrictions) is that they don't like dealing with a ton of small investors. It's easier to deal with fewer, larger ones.
In contrast, if you're a prop shop that only accepts employee money, you're already dealing with your employees.
So there's no real reason for JS et al. to set large minimums, in contrast to non-prop hedge funds.
So they're incentivized to allow as many of their employees to invest as possible.