ET shouldn't matter when you're dealing with 90th minute bets, but yes, it happens. Teams try their best to get that goal back that they're behind on and just get whacked from it.
I'm not into Olympic at the current moment and couldn't find an o/u at any other book than Pinnacle... I'll take the risk more often than not on a line like that at Pinnacle with a 10 cent line with no extra vig attached, just for these situations. Figure if the game lands on 4 or more, I'm winning the exact same amount of money I would have before. If the game lands 3, I win half of what I normally would, but if I lose, I lose about 25% more than I would have... I'll take my chances the game lands on or above 3 instead of not playing the game or loading into another book to get those odds (which were -120 by the time I caught them this morning... meaning the -150 wasn't THAT bad for 0.25 goal)