BTW, it is actually possible to use the runtime's random function directly.
The headers say the function "must be supported forever", so it's not technically unsafe or unstable or anything like that, but it's hacky. But it's possible. In a hacky way. But not infeasible.
name time std iterations warmup
-------------------------------------------------------------------------------
UniqueID.Random 40059828.000 ns ± 0.30 % 35 401728357.000 ns
UniqueID.TimeOrdered 42554658.000 ns ± 0.44 % 33 424516127.000 ns
Foundation.UUID.Random 193528251.000 ns ± 0.55 % 7 1931932069.000 ns
So that would be ~80% faster than the current implementation in Foundation. Again on the pi, with 10 warmups.
We should really fix the standard library so you can make these calls from Swift.