Two weeks ago in Atlanta, I was dropping my wife to the Airport. Atlanta traffic was doing it's thing (not moving). Google said it found alternate route that will save 7 minutes. I was like meh. Then it said 10 minutes so I took the turn. I don't know how many people did the same but I ended up spending half an hour extra in some internal road and half of it was being stuck in a right turn lane that rejoined the original highway I was on. So if I had kept on the slow moving highway I would have definitely reached much earlier than the alternate route. Bottom line is that the 'Save time' works only when the alternate route is truly alternate and not just a detour and rejoin the same highway as you will get stuck on the ramp while joining back.