Saying the won't, when they already act like they do, when some already do disconnect and come back 10 minutes later when they expect to already have been kicked, is just an opinion that ignores the reality pictured by the complains that caused the rule to be created.
Why ignore the full variety of complains related by players? This isn't just about people wanting to do dungeons fast. That's actually the least reported behavior that led to the ruling. The common complains were generally around the lines of "I don't like this dungeon, kick me" and "you suck, I won't heal/tank for you, kick me." Both of those sound like people who aren't going to do the dungeon anyways, and who would pick the lesser debuff, be it none or 15 minutes + ~60 seconds from being kicked, than remain in the dungeon, especially the second case. Hence, even if the debuff was working, we would still have a behavior we aren't going to condone by looking the other way.
It's already being treated as a minor violation with a short ban, instead of a full-blown bug exploit. And seriously, if you don't like it, consider it dully noted. The rule exists for a reason, the reason extends further than what you wish would be fixed, and it will be enforced.