IMC, haversacks and bags of holding have that non-dimensional space inside them and everything outside the sack affects the insides, just as in normal sacks.
For example, the players once were in a room with such a sonic noise that all their potions and glass objects needed to make saves. Including those in the bags and sacks.
Ie, you have a bag of holding full of potions, hit it to wall and hear them get smashed. Then, the liquid would slowly come through the sack, as in normal sack with liquid inside.
If you put a pointy item inside the sack, you might make a hole in it, from the inside. If the pointy item would be 'teleported' to some other dimension, how the heck could it make a hold in the bag?
Also, if there is something in the bags, you can somewhat feel from the outside, what is inside. If there is an apple inside, you can feel it and touch it through the sack fabric. Items effectively are inside the bag. The bag does get bigger if you put lots of items there. If you fill the whole space of the bag (instead of weight), ie, with feathers, the bag will show from the outside that it is stuffed with something.
In short, bags of holding and HHHs and others like them work JUST like normal bags and sacks, only that they take more things inside them.
Imho, if the bags would make all things inside them invulnerable to everything, the bags would be much more expensive. Safe boxes (from splatbooks) are for that.
As a house rule, If the sacks are ruptured by pointy things, the items do not vanish anywhere, but are dumped on the ground. No-one in our campaign would use the bags otherwise except for maybe some very seldom used things.
However, Portable hole IS an opening to a different dimension.
