The lighter slide allows for a proper recoil spring to keep the timing; heavier slide requires a lighter spring to allow enough rearward travel. However the cycle time on the return trip slows down due to the lower spring rate. Too slow and then the timing is thrown off enough to jam things up. Or that’s the way I see the physics.
That said, I just checked my notes. Almost 3900 rnds on my Dan Wesson Valor 5in in 9mm. (3) malfunctions. No adjustments to anything; ejectors, extractors, magazines, springs. It will eat HSTs, Gold Dots, 115 and 124 ball. It would be very shocked to know how finicky and maintaining intensive it was supposed to be. I think I’ve cleaned it two times and a wipe down. All I do is feed it ammo and give it oil to drink. It’s by far reliable enough for me to bet my life on it.
My experience has me firmly in the camp that you CAN have a reliable 9mm 1911.