Rules in Armageddon games? Please clarify

What happens in an Armageddon game in a serious match. In Yesterday’s Armageddon game Nakamura needed to win and Carlsen had a fortress, they both had about 50 seconds no increment, what would happen if Nakamura just played on and on in this dead position eventually hoping Carlsen’s clock would go. Would the director step in or does Carlsen have to play 50 moves without captures and pawn moves?

Thanks for clarifying it so precisely. Nakamura seemed to take It quite calmly when the fortress emerged. I had not quite realised that Magnus could  so quickly play 50 moves. IIRC Naka still had a pawn so possibly he could have made Carlsen play a 100 moves or maybe Naka feels it is not right anyway to play to win in that way and would harm his reputation to even try. 
What happens in serious over the board (remember those?😄) Armageddon games when the moves are not automatically recorded but reach dead drawn positions, I am assuming serious OTB games will have an arbiter.

Yep, there was 1 more pawn move available but 50 seconds is still enough for about 250 moves, there was no chance of a flag there. Yes I also noticed that Nakamura was pretty calm at the end, but I think he just really enjoyed the ride of the match. I would say without a doubt that this was the most exciting online match in chess history, and I think both players also realise that, so it was cool to be part of it regardless of the result.

I'm not exactly an arbiter  but I guess that even for OTB games it's extremely difficult to successfully have an arbiter interfere and claim a draw. I know a rule existed in older times when increments did not exist, where a player could call the arbiter if he believed his opponent was trying to flag without making any attempt to win. The arbiter would then observe the game and make a decision on whether this was the case. I'm not sure if this rule survived to this day, and even though it's a very difficult one to judge. 

I remember that in some Armageddons you get 1s increment after move 60 to avoid these situations...

I think that's the case in all armageddons...

Irina Krush would disagree.

y?

In over the board armageddons, they have started adopting the system of having a 2 or 3-second increment after move 60 to prevent these situations from happening. However, in online tournaments there is definitely no increment, your starting time is all the time you'll ever get.

https://www.youtube.com/watch?v=fNQjXHjRkNQ