Yes, it does, and it cites a potential boon for Metro-North.
Think about it this way. You're running to the edge from Harlem on the 1 to catcha Metro North. Your options are to keep taking the 1 down to Times Square/42nd street, grab the 7 or the Shuttle to Grand Central, and hope you make your train... or get off at 125th and take the 125 bus over a few blocks, incur another fare, and hope traffic isn't bad.
Hint: This is New York City. The traffic is always bad.
Extend the T all the way to the Broadway line (hint, add a third track for a shuttle train), and you get a free transfer to 125th and Park Ave, and it's a short run to get to the platforms.
Another scenario: you work in Inwood but your home is over in Morris Park. That's the 5 to the 2 at East 180 St to the 1 at 96th, or the 5 to the 4 at 149th Street to the B or D at Yankee Stadium to the A at 145th. Or you take the 12 SBS.
Extend the T and you get the 5 to the T to the A or 1, a simpler transfer plan.
A third, back to Metro North: You work in Washington Heights. You need to get the A. The most reliable plan is Grand Central, take the 7 or S to Times Square, walk to 42 St, and grab the A there.
Extend the T, and you can get off at 125th, grab the T (or Shuttle) to 125th A, and you're express trip gets cut by several stops. The only thing you have to worry about is the significant other calling you to pick something up, so please swing by Grand Central.
In other words, you get a north-of-Central Park transfer line that can cut travel times in many cases, and improve quality of overall service. I've been talking about this in consideration of getting subway service to LaGaurdia. That's the first step.