The strong meta models in SystemWeaver means that you cannot do anything that is not explicitly allowed by the meta model.
There are many advantages of applying a strong meta model.
For once, this gives the chance to precisely define the meaning, or semantics of the model: what does it really mean. This is required by everyone who will be using the meta model, both those who creates a model, and those who read the model.
Secondly it means that the model will always comply with the meta model. This is required whenever you need to do refactoring of the model, e.g. when you need to extend or constrain the meta model. It is also required for all automated processing of the model, processing like report generation, or model transformation.