There is speculation on other sites that the tent had holes, been cut and stitched a number of times on other hikes .
If the tent had a floor , which I think it did , then you would still have a tent of sorts to use in an A frame configuration, especially in the forest areas with trees to strap a ridge line. Holes, leantoos could also be dug and the remaining canvas used as a roof. Not ideal , but the cutting of a tent does not mean that the rest of the material is not a useful resource, just more inconvenient?.
However , I don't think cutting a tent on a mountain slope in the cold and most likely the dark , is a casual decision. It seems to be a deliberate choice and course of action to exit the tent , it does suggest the tent failed or the tent collapsed. The hikers, having been able to exit the tent , irrelevant as to why, now can't stay at the tent or retrieve any other survival gear , equipment or clothing. Its the fact that they can't take anything more from the tent that makes me think the tent was the least of their worries .