The lightweight Euro trains probably wouldn't save any time.
In the overcrowded NY Metro Area, "time" is lost not so much due to acceleration speeds, but rather "congestion ahead". There were days (on Amtrak) I got to Harold (about 4.5 miles from Penn station around 5.40p, and still couldn't get into Penn by [normal arrival time of] 6.00p. Just too many trains ahead.
The M-9 cars the article references are the evolutionary design that has progressed from the first M-1 and M-2 (New Haven Line) cars of the early 1970's.
They get the job done. I ran M-2's early in my railroad days, and later M-1's as a hostler in the Croton-Harmon shops.