Regarding the subject line...and the OP's year old post..."Yes" a gravel bike can serve as a road bike if you are space challenged in NYC.
As it happens, I got a Felt Breed and just did back-to-back Centuries on it. 100 in Maine Lighthouse ride a couple Saturday's ago...followed by 100 the next morning down in Dartmouth, Mass in "Flattest Century in the East."
I wouldn't normally have done this, but I planned to do the back-to-back and Hurricane Dorian was threatening heavy rain / sloppy weather. My primary road bike is rim brake, so I went gravel for the hydro disc and stable flat tires. That Felt Breed is extremely comfortable, and I was fine.