Give it up man... Arguing with the same 3 Walther super fans just results in PM's from searcher telling you to read the rules. There seems to be some good info here. Personally, I like this thread and found it helpful and have another spring on the way from a diff mfr, but trying to convince these guys to spend a dime on something is useless. They don't care, you'll never be right, etc.Designs like the M&P and XD are close enough to single action that it is splitting hairs calling it something else. The XD is placed in IDPA ESP category for that reason even the stock striker has some tiny rearward movement when fired, You will find that one that has had a superlative SA Custom shop trigger job (2.5#) or a Powder River precision job at 2.5# they both have zero rearward striker movement when you pull the trigger and are 100% cocked. They also have reduced power striker springs...
Anytime you reduce friction at the striker/sear contact point you will change the feel and reduce the amount of weight required to release the striker.
You can do this by polishing the sear/striker interface or you can reduce striker spring weight or both.
Just because the PPQ looks different internally doesn't mean reducing friction will not improve the way the trigger feels when the shot breaks.
You could do a before and after with them and they'd insist there's "no difference" and swapping the spring was "irrelevant" and "bogus". Guess you need to drink the kool-aid here and bash people to get to a point where you have no consequences for your actions, which is kinda sad really. I'd imagine this thread closes pretty quick, but thanks for the info in your OP. Much appreciated.