If there is a variant which allows higher stock clocks via a custom PCB and cooling solution, then can be fair to assume, given cooling and power as the main restrictive elements of the card and not the GPU/memory itself, that it will increase headroom in the OC department.
That is with the assumption that the GPU/memory are not the limiting factors. I think it is a sound prediction. It is an assumption that has been made many many times in the PC parts industry, that is almost always true.
Now, if this custom PCB were to use only lower binned GPUs and memory that max out at 760/1050, then it would be a false guess, but generally, the vendors use higher binned parts for higher performing variants.
Sure he was talking out his ass, but his ass might not be that stupid.