Tough to say. Not everybody makes a living planting a helo on active volcanoes. So we're talking about a pilot with a lot of local knowledge and experience.

In mountains, nasty weather comes in rapidly, but it can also go out in short order. The aircraft was intact and, given half a break in weather (icing) conditions, could possibly have self-extracted safely.

I would suspect (claiming no expertise in this area) that the dividing line comes when the pilot is certain that the aircraft cannot lift off safely (in this case, blades and fuselage are encrusted with heavy ice and weather is not improving).

My 2c.