It is easy to measure velocity these days but pressure data is very elusive. I wouldn't be surprised if the stuff that you can get from Buffalo Bore and Underwood is really 10mm +P. The pressure difference between 40 and 10mm is only 7%, 35,000 vs 37500. The case is larger so slower powder can be used but that helps more with longer barrels than the more common 4 to 5 inch barrels. Expecting 70% more power from 7% more pressure isn't realistic.

I freely admit I have never seen any pressure data from a reliable source but my gut feel is that Sig 10mm ammo is about as hot as you can get with SAAMI pressure levels. A bit more energy than a 357 with a heavier bullet out a semiauto pistol is pretty impressive even if it does not meet the original claims made by Norma. Notice I said claims. If you search for tests of the original Norma ammo on YouTube you should be able to find a couple of videos. The "full-power" Norma ammo typically comes in 150 to 200 fps slower than the numbers printed on the box. It was a lot easier to get away with inflated velocity numbers before there were lots of channels on YouTube testing ammo.

ETA:
Test of Norma 170 grain - Actual velocity 1219 fps

Test of Norma 200 grain, also about 200 fps short of advertised velocity (Skip to about the 20 minute mark):

I don't think it is a coincidence that velocity numbers suddenly decreased when affordable chronographs became available. Happened not just with 10mm but also with 44 and 357 magnums as well as some rifle cartridges.