Automakers have been doing all sorts of things relative to recycling gases for years now, and it's hard to keep up with everything on that front. I certainly don't know what Mazda's complete SKYACTIV strategy for recycling gases is, so all I can say is that what you read may, or may not be true.
However, that 165 PSI number (at 350 RPM) for "normal/standard" compression comes right from the Mazda FSM. So any effect that recycling of gases has on compression is just one of the many factors contributing to that 165 PSI spec. The only extra informational statement that's made in the FSM write-up is this one: "Because the SKYACTIV-G retards the intake valve closing timing, compression is low" I assume that "is low" actually means something like "is lower than most other engines"
Also, removal of the FP relay/fuel pressure relief is a prerequisite step specified in the FSM compression test procedure, and seems to be the only factor that could cause higher-than-normal compression test results, aside from a defective tool. As I said previously, the higher-than-normal-spec compression readings probably are not going to make a difference in the diagnosis, which comes from the extra high reading from #4.