ESRI dynamic labeling is server side labeling, which means the label was generated on arcgis server before send to you.
https://transparentgov.net:3200/googlemaps17/default?layer_id=0&layer=Protected+Areas+Database+of+the+United+States+%28PAD-US%29+v3.0¢er_lat=40.44472984406303¢er_long=-74.2462424919159¢er_zoom=18&url=https%3A%2F%2Fgis.usgs.gov%2Fpadus%2Frest%2Fservices%2Fpadus3%2FPublic_Access%2FMapServer&overlayType=overlayType_image&panto=0&dynamicLabelField=Mang_Name
ESRI dynamic labeling test use 17, 170, 171, 270, 271,
Note: Original ArcPro project must use Maplex label engine. Standard label engine would not work.
https://transparentgov.net/json2tree/esri/server2/folder.html?url=https%3A%2F%2Fgis.usgs.gov%2Fpadus%2Frest%2Fservices&org=USGS+Protected+Areas+PAD%2C%26nbsp%3B%26nbsp%3B&cross=default&timeout=10000&select_folder=6&select_layer=0
Client side labeling means the label is not generated on arcgis server, instead the label is generated in your browser.
https://transparentgov.net:3200/googlemaps73/default?layer_id=0&layer=Protected+Areas+Database+of+the+United+States+%28PAD-US%29+v3.0¢er_lat=40.44822640949279¢er_long=-74.24459293337173¢er_zoom=16&url=https%3A%2F%2Fgis.usgs.gov%2Fpadus%2Frest%2Fservices%2Fpadus3%2FPublic_Access%2FMapServer&overlayType=overlayType_image&panto=0&labelAsField=Mang_Name
Browser-side labeling test use 73, 730,