Most highway=pedestrian can be used by other modes and can fit motorized vehicles, see https://wiki.openstreetmap.org/wiki/Tag:highway%3Dpedestrian for examples. Given that hw=pedestrian is used for this situation both elsewhere in Rock Creek Park (https://www.openstreetmap.org/way/6061851) and on other similar roads that were made exclusive to pedestrians and bikes in other cities (e.g. https://www.openstreetmap.org/way/318476063 in New York and https://www.openstreetmap.org/way/27031304 in San Francisco), I really think this should be switched back to conform to the normal usage. 

Highway=pedestrian render plenty prominently in all the OSM-based apps and maps I use. Frankly, if a service isn't rendering/routing along these correctly, even with bicycle=designated, then it should be updated, rather than mistagging for the application.

(PS sorry for the delayed response, busy week for me non-OSM-wise)