It's not, except that paid adjuncts get paid a thousand or so less and the fellowship guarantees you an income. My wife is in the program. Teaching 2 classes a semester means that she takes only 2 or 3 classes per semester (and the semester she took 3 didn't go very well) but lots of students do even more. Many people have part-time jobs as well-- tutoring, publishing companies, writing centers, etc. The PhD requires 15 classes and it usually takes people at least three years and often four to complete coursework.
If anything, the teaching CUNY makes you do is great experience and training. You will suck at it for the first two/three years but so does everyone else, and at least you'll be in charge of your own class. You have a ton of freedom, but not much job security and very low pay if your adjunct job disappears for some reason (and then you can look elsewhere, but non-CUNY schools in NYC offer as little as 2k a class, which is mind-bogglingly low)
Commuting time is not too bad, since usually the two courses they give you as part of a first-year internship or a fellowship are back-to-back, and the standard is 2 75-minute classes per week per course.