Ah, but the 1911 started life as a different model. Changes were made before and after the troop trials. The A1 series changes were made in 1927, and a firing pin safety device was cancelled due to WWII. Many people see the 1911 as it's made today and mistakenly think that's what they looked/worked like in 1911. An average trigger pull on an honest to JMB 1911 went around 7 lbs, I've seen them approaching 20 due to improperly machined hammers. I've got one that came out of the Colt factory in 1913, I bought it in as issued condition and worked on 1911s for decades.
Also bear in mind that the 1911 didn't see the production numbers of the M&P for decades. To say that the 1911 didn't have some issues is not true. Heck, in the 1980s Colt was infamous for selling pistols that didn't work when NIB.
Everything made by man has had production changes/product improvements. I expect the M&P auto series will be the same.