The Bose 900 series hifi speakers and the 800, 400 and 500 series pro audio speakers are all based on the original bose 900 hifi unit from the 1960's, and the "direct / reflecting" sound concept of Dr Bose.(prof. at MIT)
The idea was to use multiple smaller drivers to gain a more even mid/ high frequency distribution (multiple smaller drivers arranged on a curve act a bit like a point source but with a wider dispersion than the normal 90 degree or so of a standard coaxial driver) The bass was the same, as that is primarily a factor of the square inch of driver area, and the distance the cone will move, this determines the amount of air the speaker can move. The original idea was to bounce the 8 drivers off the wall behind the speaker to recreate the indirect sound in a concert hall, with a single forward facing driver to give the "direct" sound.
when the live sound engineers (often for jazz events) started using them the "wrong way round" as monitors, Bose created the 800 as a "proper" version.
I guess the multiple drivers reduced the "hot spot" that can cause feedback problems with live events.
Thats the potted history.......
The problem with this sort of deign occurs when balancing the stiffness of the cone and the other design factors that fight each other to get bass and treble off the same driver, so the EQ unit was invented to compensate.
So yes, it adds bass and treble, but it is an essential part of the speaker design, else the frequency response will be anything but flat.
The old adage of " no highs no lows , it must be bose" dates back to the early days of the 802 when folk saw the 200 w rating on the cabinet and matched the amplifier to that, not realising that a 500w amp delivers the extra current the system needs to sound good. As long as you don't clip the amps, a 1kw amp driving a couple of stacked pair of bose 802 can sound remarkably good against the current opposition, especially so when you are comparing a basically 1960's design with the latest.
Yes you need a sub (thats what the 302/502 mb4 bins are for!!) to get real lows, but the same would apply for most 12 inch and horn cabs.
The latest digital controllers not only have presets for practically every bose speaker, they are also a lot quieter and more accurate an eq curve, and also include some important additional processing such as limiting.
Hope this helps to give a broader picture that is relatively unbiased!!
YMMV.
disclaimer.... I worked as the system design engineer for Bose for a couple of years about 20 years ago....... but do not own any bose gear these days!!