I assume the original author meant to say: draining /dev/random does not affect the cryptographic quality of the random numbers produced by both devices.

But yes, since there's only one entropy pool, attackers can drain /dev/random, causing other programs that rely on /dev/random to block.

All I can say is: on newer kernels, attackers can still drain the pool by using the getrandom syscall, so unless you block that syscall, not mounting /dev/random does not increase the security.