Lots of people did the LEO/DA only conversions to their USPs or a hybrid of the USP Match trigger with components from the LEO trigger. There is debate about which trigger set produces the "best" USP trigger. Its possible that is what is in yours.
If I remember correctly, straw man only comes into play if you're intentionally purchasing a firearm for someone with full knowledge that they are not allowed to possess one. That being said, a lot of shops get fidgety at any mention of you purchasing a firearm for someone else under ANY circumstance.
If someone who can legally buy and possess a firearm gives money to someone else to buy a firearm, that is also a straw man purchase. And, buying with the intent to sell (as in “hey go buy this gun and I’ll buy it from you”) is also a strawman purchase.
