That's not what's going on here. You're referring to the braindead behavior that `/dev/random` can block because it thinks its entropy pool has been depleted, which is of course dumb because once the pool is sufficiently full it can't be emptied. What's going on here is the scenario where the pool genuinely is empty because it hasn't been filled yet. This can only happen at early boot, but is a genuine thing that happens; unlike it becoming empty later.