The opposite process also happens, though... not just a 3- and 4-story residential buildings demolished for large residential towers (plenty of that in NYC) but single-family brownstones carved up into smaller dwelling units.
The map caption "Conversions Have Erased Some Gains in NYC's Housing Stock" would make a less deceptive headline. The map shows data from a defined timespan ("between 2010 and 2021") and shows that there's not a single community district that hasn't added housing units. The headline, meanwhile, refers to a vague "70-plus years" timeframe. That's long enough that you could probably find hundreds of buildings that have bounced between single- and multi-family several times.
And in fact the underlying research characterizes any building that was ever recorded as multifamily and currently isn't as a "loss." I fear it risks romanticizing the 20th century's cramped tenements.
(And again, just to be clear, I find conversion of viable multifamily buildings into mansions generally repugnant.)