The cats you are referring to are called warm up cats, sometimes called pre-cats. Almost all cars have them these days, but for some reason, a lot of Nissan owners and mechanics believe this story. One other factor in this story that you didn’t mention is that it mostly affects the high performance engines.
Nissan uses a long overlap on the exhaust valves that extends well into the beginning of the intake cycle, that is how the negative pressure is created in the exhaust manifold. It is intentional so that some of the exhaust gas is drawn back into the engine. These engines use this in place of an EGR valve.
I am not going to try to validate this story, my son has one of those Sentra Spec-V that is subject to premature oil consumption. His came brand new with a reman engine. The car was recalled off the dealer lot before it was sold to get the engine replaced. All Nissan did with these was disassemble them and replace the rings.
One thing that Nissan did acknowledge was that they got hold of some “soft” rings and they are blaming the oil consumption on that. Now, to me, that is a believable story.