I will have to agree with that. For beams you can get away with loads of raw power in a HUGE beam and scan considerably slower (~20-30kpps) for effects overhead, whereas you would want pin-point beam spots and perfect white balance for graphics in a FAST, narrow scanning package.
With proper overhead effects, people will not notice you're not going 'into the crowd'. This may be different on a dance party than on a more sophisticated show like in a theatre or a corporate presentation, but I like well-designed overhead shows a lot more than shows that just blast a dumpload of beam effects into the audience.
If you have dedicated overhead beam projectors, you can do some very clever positioning with them in a lot of crazy directions, for example, one or two projectors pointing straight down from the top stage edge creating a 'virtual wall', grid or force field between the audience and the performer. Also, with a few bounce mirrors something like this can be even more dramatic, where the graphics projectors remain more fixed and just do what they are designed to do -- project graphics in a perfectly aligned, straight fashion.
Beams need lots brightness because they travel through free air and scatter off fog to be visible. Graphics projectors can profit from a reflective screen, so a multi-watt projector doing graphics is little use in most cases.