/dev/urandom provides an unlimited stream of random data, the output is based on truly random data and doesn’t block regardless if the entropy pool is depleted.
It’s not the same as /dev/random which only returns random numbers from the entropy pool at a limited rate and can block if the entropy pool is deplete.

By using /dev/urandom and cat we’re blasting random data at much faster speeds then what /dev/random & dd are capable of which increases our chances of triggering a bug by quite a bit.