Of course you probably already know this, but I think the root problem that OP is driving at here is that if you use /dev/urandom then you risk getting predictable values from /dev/urandom at startup[1], e.g. when initializing your server's SSH keys (or whatever). I seem to recall this being the root cause of thousands upon thousands of home routers being having weak keys. As such, it's important to point out.
[1] That is, before enough external entropy has been gathered.
Yes. Yes, it does... but it's not transparent to userspace, which I think is what tptacek was alluding to. (And, frankly, is how it should be. However, the Linux kernel maintainers are absolutely fanatical about backward compatibility for userspace, so here we are with a new syscall.)
[1] That is, before enough external entropy has been gathered.