I was not confusing the two. AFAIK we do have truly "random" sources, and thats what I was referring to.
I was also referring to the fact that the linux RNG uses multiple entropy sources-- including intel RdRand-- in order to address issues in any one of them. Theres a write-up here which indicates you CAN mix sources without losing entropy:
More simply, if you XOR truly random source A with compromised source B to get seed C, an attacker could know all of the output of B, but he would have no way of determining A or C-- he literally has no additional information. This is pretty trivially proveable, and if it were not true stream ciphers simply would not work (One of the values is known, but the other two cannot be determined).