Yes, and Linux has done it for years. The problem is whether or not RDRAND should be trusted in the absence of sufficient estimated entropy that it should be used to unblock the CRNG during the boot process. This is what CONFIG_RANDOM_TRUST_CPU or the random.trust_cpu=on on the boot command is all about. Should RDRAND be trusted in isolation? And I'm not going to answer that for you; a cypherpunk and someone working at the NSA might have different answers to that question. And it's fundamentally a social, not a technical question.