Home Switch Triggers on On or Off?

[GeckoSub]

So, newbie here setting out to do a new build. I am almost certain I will go with UCCNC + AXBB-E but have a few questions as I am about to start buying various hardware.
Excuse the lack of proper lingo but will do my best.

How or rather when does UCCNC sense the home switches? I was told some software turns the switch on, then off and sets position on the "off point" of the switch, not when it first "turns on"?
If that's the case, I was also told, the hysterisis between the on and off point or rather the repeateability if the off point and not the on point is what's important to get the most accuracy and repeateability.

[ger21]

Home is when the switch opens while backing off of it. UCCNC allows you to set different speeds for each direction, so you can back off very slowly.

[GeckoSub]

Thanks for confirming this Gerry:)

Also, am I right in thinking I read somewhere here that I can't use the zero/indexing pulse of a stepper to home to?