I think this is an erroneous assumption that gets many divers in trouble. The bottom line is,
you always have the final say on making a particular dive and particular dive profile with the equipment at hand. If the equipment you have with you is not adequate for a particular dive,
you and only
you have the choice of whether or not to make that dive. No one else can make do something if you don't agree to it. Your safety under the water is solely your responsibility. Yes having a buddy gives you some options should trouble occur, but you should always avoid trouble to the best of your ability...even if it means telling an instructor or dive master off for something stupid like expecting you to make deep dive on a mere 60cuft tank.
Now I'm not saying this to rail on you, but to make sure you know your safety is in your own hands and you have the right to call any dive at any time for any reason.