Silence is a response in a way, and it means "NO". Player has to give consent, as rule says "explicitly".
Players follow the rule and have no problems. When they start to go into philosophy about how their OS is more important, they get a wake up call in a form of 5 days ban, some realize, some make huge dramas and even make a ban appeals, then staff shows mercy, remove their last day of a ban.
Everything is fair, this is how to behave in random dungeons with random players. Only "loophole" would be if everyone says "yes" and then deceptively takes screens, leaving out proof their own consent - to get someone banned.
I have seen probably hundreds of items getting disenchanted, item that I needed for OS. If someone wins greed roll, I just ask them to trade me the item, 99 of 100 times they do and are happy to do that(and that same player would probably report me if I NEED). They even ask "why you didnt just NEED?" - why? because I don't want to get 5 days ban, real simple. After the fact when everyone did things fairly people are happy to "help out", but they are extreme opposite if you take their chance without their consent.
I was farming arp trinket in TOC normal dungeon, made a group, explained everythnig, I was a tank, but rolled for that trinket and also all tank gear. Everyone was "yeah, sure" or left the party. Was fair, nice and smooth, everything was clear to everyone. No problems. Didn't have to impose my will on anyone unwillingly. So here it is - player wants his OS gear, create group, negotiate and do whatever.