Thank you that expiation... I had no idea as I own the 18-80 CN-E, I assumed it was along the same lines.
Since there is a gap that both the broadcast/cinema people have crossed, for me it seems that Canon actually goes out and beyond to market the Cine-Servo lenses for two distinct markets (broadcast, with the "CN7X17" type of name; and cinema, with the regular "17-120mm" type of name), while the Compact Servo lenses are marketed more as a "hybrid lens", with tech that came from cinema (being parfocal mostly), video (servo unit) and stills (autofocus and IS) lenses in one package, being cheaper compared to the Cine-Servo lenses, but a little higher price than top-notch L-glass EF lenses.
I get what you're saying about the Compact Servo lenses, but I'd go out on a limb here in saying that being T2.8 would meant that either they'd have to drop the servo function and lower the zoom ratio (such as the Fujinon MK series, which has a 18-55mm T2.9) in order to stay compact or drop the idea of being compact and go full blown bigger (which is the Cine-Servo series). Even if they tried to go "in between", they'd probably end up with something alongside the Fujinon XK20-120mm, which is a T3.5 lens being a lot bigger than the 18-80mm.