When the spindle is properly grounded, i.e. pin 4 to ground and the chassis of the spindle is grounded to the the internal pin 4, then you do not need the magnet for the touch probe. The chassis of the Makita router, by itself is not grounded, it only has the 2 prongs(at least the US version).
Here is a good/short thread/explanation… Touch probe/Spindle - What did I do wrong?