No, it's pretty much used on tech race skis, especially GS, not for any all mountain use I know of, except in the process of correct tuning bevels to get them at least level.
It may be that progressive base bevels are no longer used in racing much. I stand corrected if so.
But it really works well for anything hooky or grabby with a race ski. To get the ski just right, varied for each racer, ski, and situation, not some standard amount. By experience and feel, with both race techs and racers (or normal skier who tune their own skis well).
And base bevels being un-level, or having reversed progressive base bevels (steeper underfoot, more gradual at tip and tail) are very common on current race skis, and all mountain skis also, as poor tuning that can be easily corrected, either making the base bevel level or slightly progressive in a right way - underfoot flatter. This is not "extreme" - it's just good tuning.
And edge de-tuning is not needed as a result, ever - except maybe for extreme freestylers and such. Base bevel around the tips can be varied to get perfect tunes - much more efficient and effective than de-tuning. Standard tuning practice, for decades.
This quote is also an over generalization: different progressive base bevel tunes handle differently, are appropriate differently. A good one, a right one, does not result in loss of grip; and a different such tune optimally, routinely, would be used for situations that needed more grip than ones that needed less: from experience, individualized, skier to skier, ski to ski, particular race to race, conditions of the snow mattering also. I only bring this up, in terms of primary use, because you statements are so broad and over-generalized - and incorrect, near as I can tell.
Where to start?
Guess I'll just comment on the first one, skip the rest (except I pretty much agree about Head and Atomic feel):
The zero base bevel is not dangerous a bit, with a bit of familiarity. At one time,
everybody skiing, beginner to elite, and definitely everybody racing,
used a zero base bevel as standard. No one then used anything different. For, what, forty to fifty years, in the case of my generation
(longer for earlier generations)? No problem. Normal and easy.
It's what you are used to: in this case, a very neat, immediate response putting a ski on edge. Not a big deal. It was always normal.
Again, no problems resulted. For generations of skiers, including myself and many others - still, if I'd want to.
(Actually, on FIS slalom skis, Ligety, and many others, used/use a zero base bevel the whole length of the ski as standard - he only used the zero to .5 progressive base bevel on GS skis. )
I can testify as a mere mortal, that I have no problem I've ever been aware of on a level zero base bevel ski:
I still have a pair of functional, very old, straight, men's FIS GS skis I once raced on a long time ago, that I take out now and then and really enjoy still, that has always had a right angle edge, flat base. Fun ski. If you tried it, you'd experience it for yourself, probably easy once you got used to it
(probably in a few runs, dunno).