I expect they say "not for LEDs" to cover themselves for customers with CC units,
they probably dont want to argue the difference, easier to just say "no LEDs".
Re the LED dimming level, they could have a tailored response for incandescents
which have a very non-linear brightness/current curve. Up to about 50% a bulb
would hardly glow, so a tailored dimmer would cover say 40 to 100%.
LEDs would half-light at 50% which I think is what the lads were saying.
Cheers
Phil