100Hz is a bit too much. Didn’t those people say to highpass everything EXCEPT the sub and kick at 100Hz? That would make way more sense.
I cut everything off at 30Hz and I think it’s fine like that. You lowcut the signal so you get just a bit more headroom in the mix, but if you’re not really running out of space, then it’s just a matter of habit to highpass at 20, 30 or 40Hz.
In the end, it has to sound good! Otherwise it would be pointless.