WKF (and all other organizations using basically the same point rules) are very distinct from american foam foot-fencing. I cannot say for the american point karate point of view, but the WKF point of view is that they do not want to be lumped together with the foot fencers.
WKF point karate
This is what the rest of the world regards as point karate
It is all about distancing drawing out attacks, countering, counter-countering and timing. hitting without getting hit. Machida elusiveness
foam foot fencing (american style point karate)
This stuff basically only exist in the US.
I honestly have no clue what this is about except standing on one leg and waving the other in front of you.
(If it seems like I despise this, it is because I do)
As for kempo and kenpo they are such a broad group so that you simply cannot group them together as one for anything. Some do various point karate versions (including the foot fencing above), some do full contact (including knockdown/kyokushin variants), some do other stuff entirely.
You have to look at each individually.