hmm, the balljoint itself is pressed in , but it sits tight due to that bracket arrangement you mentioned.
Not good that its only fixed at the one side
Strange that your mechanic didnt see it when u were having the controll bushes swapped..
If you are thinking replacement arms then get E30 items. The balljoints are pressed in just like the E36 M3 items, but are actually cheaper than the E36 regular arms..
Ball joints are an E36 weakness.