I've been watching a bunch of games on Jinteki.net, and I'm seeing players make a run and then jack out after the ice is rezzed. I thought you could only jack out when the ice is "approached", not "encountered".

People will often use 'jack out' instead of informing the other player 'no break' and waiting for the Corp player to hit 'end the run' when playing online to expedite play as it usually has the same effect.

However there are some cases (playing with Au Revoir for example) where the distinction matters, and you are correct that in these cases the Runner should allow the Corp to resolve the EtR if they cannot/do not with to break the ICE.

I think this is more of a convenience of online play rather than a strict demonstration of appropriate timing. Even if the ice doesn't end the run (or does more than just that) then the Corp player can fire off the harmful subs even though the runner isnt on the run per se.