Nearly all Ferguson implements attach to the Top Link connection, only a few special implements use the lower hinged pin. A Post Hole Borer is one, the Trailer Hitch is another and draw-bar stays for the linkage draw-bar, but there are a lot more. It is just a stronger attachment point and was used on the old Grey tractors right from the very early days.
You can safely use the Top Link connection to attach your Ferguson Mower without any problems as it is made to attach at this point. Regarding Draft Control, obviously you don't use it as it is not running in the ground, so you use Position Control if you have a 35 type tractor, which will hold the mower at whatever height you need to set it above the Ground and you move the Draft Lever down to the bottom of the Quadrant out of the way. If you have a 20 or 30 type tractor, then you use the Chain in the center of the mower draw-bar, hooked into the Rack on the Top Link to hold it at the correct height (PTO shaft Level) and lift and lower with the Quadrant Lever as normal....... John(UK)...email@example.com