TVM starts with the assumption that there are already a lot of ongoing economic activities.
There is a need to start keeping score in a meaningful way as soon as possible. One way to do this is to keep track of just some part of the economic activity in the community ... preferably some part that is important. Things that are not changing fast may be taken into consideration later.
There is no value in keeping detailed score about things that are routine and not changing ... at any rate for the time being. TVM is modular so that it is possible to start keeping score in a meaningful way on things that are a priority. TVM allows for detailed tracking of just some part of the economic activity in the community ... without the need to do it all. Things that are not changing for the moment may be taken into consideration later.
Caveat. To use the sporting analogy ... the game is already going on. How do you make some useful contribution as a scorekeeper when the game has already started? One way is to find out what has already happened and start off with the score as others are reporting it ... and then to keep score on a continuing basis from that point on. This seems reasonable.