Alphago isn't programmed to think of that as a mistake (i.e. the team wouldn't be disappointed if she did it). It really only cares about W/L.

I can't believe they would be told not to, or that Lee would abide by it in this match!

Now, I'm not good enough to evaluate if this seems likely, but I could understand that AlphaGo (especially if it was winning) avoided Kos, since they are high variance situations.

Looks like the other way round - single machine alphago wins 77% of the time, when it gives 4 stones handicap.

The number of serious games above 19x19 is basically nil, so the difference is a bit misleading (although it's definitely more common in go).

Ditto to me. Seems strange - maybe white tried suicide?

But it doesn't seem possible on the web link for the player to pass and then see the score?

No, you'll have to estimate or count manually, as it stands. An "end game now" button sounds like a reasonable fix, though.