These changes are incorrect. Boroughs are the proper place type for the next-smallest organizational unit in a municipality, what traditionally Americans would call a "neighborhood".

From place=suburb :

"OSM's usage of 'suburb' is different than that used by North American English, where a suburb is "an area, often residential, outside of a central city". Often these suburbs are distinct settlements and will be tagged as place=village, place=town, or place=city, depending on factors such as population. In contrast, a district, ward, or borough of an American or Canadian city would best be categorized as place=suburb."