It's related to data sovereignty laws, I'd bet. South Korea is very VERY paranoid about the GIS data about the country, to the point that there are laws that basically say "if you get GIS data from Korea you are not allowed to export it in any way." The Korean language OSM page for mapping SK is an interesting place to start:
https://wiki.openstreetmap.org/wiki/Ko:첫_걸음It would not surprise me if "Find My iPhone" would have to be completely and totally rebuilt from the ground up in SK and run on SK infrastructure in order for it to not be considered exporting of survey data.
Every map of South Korea must be served from... South Korea up until a certain point. You can see this if you open up Google Maps and zoom in.
There's a special version of OSM that has military bases conveniently ignored for the purpose of in-country usage: https://tiles.osm.kr/
Here, South Korea is only visible as a series of indiscernible land shapes -- North Korea has more detail: https://www.google.com/maps/@35.7704632,128.4760504,6.94z?en...
Zoom in one level and if you're on a particularly bad internet connection, South Korea will slowly chug its way into existence: https://www.google.com/maps/@35.7701121,128.6819944,7.94z?en...
Bing's view of South Korea is even weirder, since they don't use vector graphics for that part of the world. You can see where the labels will overlap, with English labels being covered by English vector labels: https://www.bing.com/maps?cp=35.883894%7E127.933616&lvl=9.0 ( https://i.postimg.cc/SRnZfgHC/image.png )
At some zoom levels in Bing Maps, you can see they're using a VERY old render, sometimes old enough that destroyed buildings are still visible or routes that no longer exist are still there. It uses American-style highway signs and with a high resolution screen such as a modern 4K panel you can easily see where the bitmap graphics that have been hauled over are falling apart.