Yes, location data is stored on the device.
https://file.nostrmedia.com/p/4eb88310d6b4ed95c6d66a395b3d3cf559b85faec8f7691dafd405a92e055d6d/b59c2da8123ae2550e1f379c4cfc3394a15416c3aa13e88d47eec09c9ffe94e7.png

Good question. Checking on device sync in the matrix forum now. Will get back to you when I hear something.