Most new better quality pea type whistles now use a non absorbent pea material that does not collect moisture and cause, IMO, the almost mythical freezing that would prevent the pea whistle from working.

I grew up playing organized league hockey and also unorganized outdoor rink/pond hockey outdoors in temperatures down to -20 if not more sometimes. When we did have a "Ref" for the outdoor game the old style pea whistles always worked fine with constant use while exposed to the these cold temperatures.

I have never heard of any old style pea whistle not working when needed in a survival situation. Remember the best survival gear is what you have with you when needed. If all you have is a old pea whistle, it is much better then the alternative of no whistle at all.