Discussing changes in the weight of the path resulting from path_between for agents on a grid

[lesquoyb]

Recently there has been some changes in the operator path_between and the weight of the resulting path has been changed in case of agents on a grid to be processed in the same way as the other cases.
That being said the outputted values are now different than, and with @ptaillandier we are not sure if the new or the old way is "correct".
For example here:

In gama 1.9.3 the blue path had a weight of 6, and it is now 7 with the new code. In general the new weight seems to be 1 more than in the previous version. The only exception that I found being this case with all the points in the same cell of the grid:

Where in gama 1.9.3 the weight was 3 and in the new code it is 0.
What do you think the weight of the path is supposed to represent in this case ? (maybe @chapuisk you have more concrete examples?)