Don't the dealer techs simply relocate the kick sensor per installation directions? Even if not, it still works in the original location. I guess I've never heard of anyone taking it out and leaving the open plug.
The instructions (
http://toyotaparts.sparkstoyota.com/install/PK960-42K10inst.pdf) say "Conflicts with the Hands-free lift gate option", i.e. the kick sensor. Thus, Toyota says it cannot be added to a car with the kick sensor. But many dealers do it anyway, and just unplug the kick sensor and remove the kick sensor mounting brackets,
But Toyota has no instructions for doing that, and there are a number of posts on this forum that shows how to move the sensor, but those are not official Toyota recommendations.
There have been a few posts on this forum where members have complained that when water gets into the open connector for the kick sensor, they get strange electrical errors.