And YOU know all that for sure, because......
Well here's a link to a forum(yes a forum) where someone mentions Larry Vickers who says the pistol failed miserably. Apparently LAV posted that on social media. I've also heard from other reputable sources that what LAV posted is correct in that the 320 had issues and failed the testing, even though the RFP was practically custom tailored for the 320 to win.
https://pistol-forum.com/showthread.php?23557-Sig-P320-quot-failed-FBI-test-miserably-quot
Big green needs a lot of pistols and likes them cheap. The 320 does an alright job and it was cheap, rumoured at $207 per gun. Keep in mind the MHS contract was for guns, magazines, parts, holsters, and ammo...