Fernando
You point is taken
The idea concerning certification (limitation section of the manual) and uprated same engine model is to control interchangeability of parts between models. Obviously if there are the same model with two different overhaul lives there would be a big problem in sorting this out.
For various reasons (to avoid extra certification testing) the engine manufacturers try to avoid changing the model number for even the smallest changes in the power curve. But the arguments are examined thoroughly by the CAA/FAA when it comes to commonality.