It is lighter and simpler to not have a separate switch and there are plenty of good headlights (including other Cyo models) that don't have a daylight running mode.
Absolutely, although when I bought it the 'T' version was the only Cyo Premium that anyone had in stock (I reckoned it didn't matter, since it was going on the Brompton anyway). It'll be a shame if all the newer lights end up with a daylight mode like the IQ-X, as that negates the main benefit of the sensor. I suspect that's the way things are going for marketing reasons.