The average Cirrus has zero ice protection - as has the average TB20.
I am not sure you are correct.
Since Cirrus introduced wet wings, tail and prop. apparently very few owners havent taken them up on this option. You see few SR22s in particular without this system fitted. Whilst until recently it was non approved (and the approved system has a larger tank, dual pumps, screen spray bar and a high speed flow setting) the previous system worked very well for "inadvertent" encounters; I have no doubt more than a few pilots use it when they expect to encounter ice. Of course whether or not these particular aircraft had it fitted I dont yet know.
A wet prop would clearly be inadequate and is really not very much help in the sort of conditions that might have been prevailing at the time but Cirrus have never gone the route of offering stand alone prop. protection - it is either full airframe or nothing.
When I have encountered ice a wet prop. is of very little help reducing only the time in which to make your escape, however the Cirrus wet wing system works very well. Diamond use an identical certified system on the 42. I had occasion to remain in icing for well over an hour and the sytem dealt with the ice that accumulated before it was turned on very well indeed and prevented any accretion what so ever - just dont forget to turn off the bar before starting the approach!