I don't know of any clients who use them, but I have. I assist as course manager for a couple of half marathons that I also measured, and are run on Rails to Trails and recreational paths. Several splits are in the middle of nowhere. If you use the decimal format for your coordinates, it is easy to reenter into Google Maps and Maps will take you to within a few feet of your split. Close enough to find a tree, faded paint mark, nail or other feature. I also find it easier for a half marathon or shorter course to simply calibrate my bike and ride the course from start to finish and freshen the marks.
Example: A GPS locater app on my Samsung S10 gave me the following coordinates for a round storm drain near my house of: (41.820312, -88.169990). The Solocater app for the same point gave me (41.820340, -88.169985). If you enter either of those in Google Maps, it will take you to within about 4 meters of the storm drain on the SE corner of Main and 2nd Street.
GE coordinates for the same storm drain are: (41.820302, -88.170000)