After reading all of this thread and admitting not to have seen the incident occur on tv, my opinion is that a runner shouldn't be allowed to pick up and pass hydration to a teammate that is under so much stress that they can't look after their own needs and the first bottle taker not being the first runner to take a drink from the bottle.
I realize that the current rules don't speak to this advantage that a runner with out friends suffers a disadvantage from. But it does seem to smell bad from the fair sportsmanship perspective. Since the current rule is vague, no harm no foul.
Hopefully in the future the rule will be spelled out very clearly. And perhaps teammates can be easily identified somehow so race marshals can keep an eye out for teammates trying to stretch the rules of sportsmanship and fair play.
Also no warning for first offense. Both runners if the second bottle holder drinks first should be DQ'ed. If the second runner doesn't drink and discards the bottle then only the first runner gets the axe.
I believe this is fair and levels the playing field for all athletes.