Because it's the Bronx
There are special rules when this occur ~ even though you may have a right to a 1 ft lot line under a clear reading of the rules, and might even get your plan approved, you had an obligation to check or zoning on the adjacent property lest there be a contextual zoning rule ~ which there is ~ else you might end up having to knock down your building.
I may call this homeowner's shyster lawyer next week to see how he's progressing on making a deal on, let's say, $2,000,000 ~ before the high bulk building owner has to buy ALL the houses on the adjacent zoning block.
A neighbor didn't like my backyard garden. She called every state agency she could to harrass me. None of that worked when i called all of the visiting bureaucrats up to come and look at her "height of bulk' violation ~ they came ~ she spent untold thousands getting out from under that problem ~ which would have required her cutting of a good 1/3 of the part of her home facing the mainstreet.
That was a 'contextual zoning' rule.
New York may be more forgiving but somebody just got caught.