While i am applauding and supporting whole leaf shutter discussion - there is nothing that stops you from shooting f2.8 in bright sun with flash - just use ND and real flash
That's exactly right. I noted the use of ND filters as one of the (several) workarounds to not having leaf shutter lenses.
But it comes with the obvious drawback that if you wish to shoot using the viewfinder your view is now dimmer. This is especially problematic on dSLRs which already have (compared to medium format) dim/small viewfinders. To get the effect of 1/250th sync from a 1/125th-limited body only requires 1 stop ND filter, but to achieve the same look at native 1/1600th sync would require 3.5 stops of filtration, which is quite strong. A strong ND filter can also wreak havoc on some autofocus systems.
If you're comfortable shooting in live view (and your camera supports shooting from live view in an elegant way) then using strong ND filters may not significantly effect your workflow, and may be a great option for you. If you prefer to look through an optical viewfinder then the cost of a strong ND filter may be far too high.
Clearly this option is with little downside if you're only needing to shift the effective sync speed by a stop, or maybe two, but drops off in utility depending on how far you want to go.
In fact the technique can be used even WITH leaf shutter lenses. A 2 stop ND filter in front of a Phase One kit would yield an effective sync speed of 1/6400th with standard strobe units, allowing you to shoot near night-level light even wide open at noon, without having to bring a huge quantity of strobes (maybe two B1 would suffice).
Another option is to use the flash systems which change from flash to effectively-continuous sources of light, which allows some crazy fast sync speeds. But the cost in that case is the drastic drop in effective power output of the flash, often requiring several flashes to be combined just to get a normal amount of effective output back.
Nearly all photographic problems can be solved any number of ways. Each way will have upsides and downsides (including cost). A great photographer can take a great photo in nearly any situation. But when one can eliminate an artificial technical limitation, it (IMO) naturally opens creative options. No one would
choose to have their sync speed limited, so we are only arguing about the relative value of a higher sync speed vs the relative cost of achieving it by various methods (ND filters, working in darker environments, pseudo-continuos light sources, LS lenses etc).