My understanding is it did pass the M17 trials with the original trigger and the change was made afterwards.
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While the MHS passed DoD’s TOP 3-2-045 test with the trigger currently in the commercial P320, SIG proposed an enhanced trigger via Engineering Change Request E0005. As it didn’t result in additional cost to the government and only improved the firearm’s performance, M17s currently being delivered to the US Army have this trigger. Additionally, this trigger also eliminates the “double click” felt during P320 trigger pull.
http://www.thefirearmblog.com/blog/...ry-upgrade-pistols-will-receive-mhs-triggers/