Hey Jim,
The top connector does not interfere with a full stroke of the jack handle (if it did the thing would not work at all). It does preclude the use of a handle keeper while it is in place, so while you are using the device you need to employ something else if you want to leave the jack and secure the handle vertically. I haven't faced that issue; if I did I'd simply dedicate a loop of One Wrap or a short bungee to use as a keeper. The top connector comes off for storage, so it's not in the way then.
The fact that the top connector doesn't let the handle hit the main jack beam could be considered a safety factor on its own - as you know, one of the risks of Hi-Lift use if you don't pay attention is pinching a thumb or fingers between the handle and beam while stroking. This prevents that, although you could still get pinched if your hand on the handle was in exactly the wrong spot and hit the device itself. Again, not something I've run into.