At least the ones I have messed with. ('Messed with'..... doesn't that sound professional! LOL)
The sector gear has a high spot in the exact middle of travel and the gear lash will be at zero only at the center of travel when properly adjusted. Too tight of a lash adjustment off to the side of center of travel will result in a binding condition when the sector gear turns through the center.
This center of travel and the proper adjustment of the gear mesh for zero lash and proper torque at center should be found, and the straight-head alignment of the steering with the tie rod adjustments and centering the steering wheel should be done with the steering box at this point. And due to machining or parts variations, this center-of-travel point may be a bit off of halfway between the ends of travel, so it should be found independently of the end of travels. (I.e., don't just count the turns end to end and go halfway between.)