You will want to follow the directions that came with your GE panel for torque specs for its neutral lug.
Yes, there is a reason not to use it. It costs more than Model #TLK20CP, which is just $4.08. This item will accept up to 4/0 cable, whereas the $4.08 version will accept up to 2/0 cable. If you will not be using cable thicker than 2/0 for your ground wire (highly unlikely), the cheaper one will do just fine. Any subpanel should have separated ground & neutral bars, as you planned to do.