pixel_player75208944 Yes. You only get the experience bonus if you completely clear a mine. For older events with the challenge inside the quest mines this is quite difficult for lower level players to accomplish. In newer events,the challenge mines are completely separate from the quest mines.
As @Alex_Clover mentioned, if you want to get enough tuxedos for the special item achievement you will have to do some of the hard parts, but not all.
