Interesting just tested it ingame and yes that is how it works, i never knew you needed to place it directly on the mine with a prompt. The actual function is not well explained ingame.
I also attmepted to use them for both 'false flags', or to mark a freindly side of the road while the potential hostile side is unaware, and just assumed they didn't work right or got cleaned up on garbage cleanup.
Edit: So you can still do 'false flags' and marking roads before hand, but it requires extra steps. You have to place and arm a mine first, place a flag, then disarm the mine and pick it back up. The flag will stick around if done this way.