The Sig optics are the same as a 507K (if I said C earlier, I meant K) which has shorter front posts and no rear posts. An RMSC will fit a Sig/507K footprint but not the other way around.
Many (but not all- non 30 Super Carry Shield Plus and Glock Slimline MOS have all 4 posts) "RMSC" cuts are actually 507K cuts.
Point being, the RMR is too wide and Sig is always going to support their optics, but if this is the same RMSC cut that already exists on the P365, it will allow you to direct mount a Holosun EPS, EPS Carry, SCS Carry, SCS 320, and a few Sig optics.
ETA: looks like Sig is calling it the "Compact (RMSC)" footprint. Which further leads me to think its the same 507K type cut on the 365.
I'm not trying to argue with you- instead trying to point out why the 507K cut makes sense and is good news not bad news.