Statistics is a very demanding job. Not only do you have to give points for every stone, you also register the type of stone (draw, take out …), the curl (in or out-turn) and place the stone in the house for the shot-by-shot coverage you will find for many of the major competitions.
There are guidelines (mostly by the providers of the statistics software) how to give the points for each stone. Most important is what was intended, how (well) was this achieved and could the player have done better. You also need to consider the other stone in play. Is there a guard you could hide behind, should this have been a freeze, etc.?
In your specific example you would probably give 3 or 4 points. As a rough guideline you can say, ‘be in favour of the player’. You are right, you do not know which is closer, but you also do not know what will happen with the next stones. The question ‘will this stone give a point at the end’ is only relevant for the last stone of the end, for the others it is ‘was the stone played as intended’. So in your case the objective being a draw into the house (achieved) and laying shot (not clear), you will never get 0 points, most likely, as I said, 3 or 4 points.
You also have viewing limitations, when doing the stats you will almost never be able to see the house from the top like this, you always have a slant view. You are seated behind the coaches, media and timers, as high up as possible, you do have the best view in the arena but you also have to work hard for it ;).
No statistic is completely neutral and objective, you will find many occasions where players would get different points from different people doing the stats. However in general you would expect these differences to average out over a game.