I see that come up, again and again, as a recommendation on these forums in thread after thread of 'Suggest to me a soft poly'.
I honestly don't think people have played this string extensively if they think its a soft poly that's comfortable on the arm. It may have been the case a few years ago compared to the earlier generation polys, or the likes of Lux and Revenge, but I would never recommmend PLII to anyone looking for arm comfort, and certainly never to anyone with arm problems.
As I said in one of the posts above, I used PLII 18 for over two years, and whilst I admittedly, was playing alot of tennis during that it time, it is a string that's hard on the arm.
What I suspect is happening is that they're either playing a larger sized, open patterned racquet, playing infrequently (say once a week), keeping the string in their racquets for a significant period of time, they're stringing very low, or its simply lost alot of tension. At normal tensions, in say a 95/98sq" stick, over the intended playing life of the string (and we're really looking at the lower end of 8-12 hours), there's no way it could be described as a soft comfortable poly compared to what's currently out there. BHBR, BHSR, Black Widow, Scorpion, PH18 for example, are just a few strings that are significantly more comfortable.