Maybe, but you're missing the other use case - that in the future you'll need an extension requiring geometries that are considered invalid by the current set of rules, forcing you to update all tools processing the file format to acommodate the new extension.

Keeping storage and validation as two separate steps is a more flexible design, preferable on platforms where data is entered by a large number of users in a complex domain that is not easy to model inambiguously.

Think of Wikipedia and what would have happened if its text format had only supported grammatically correct expressions without spelling mistakes, and without letting you save templates with any errors. The project would never have attracted the volume of editors it took to create the initial version with millions of articles, and the product would never have taken off. In an open project with data provided by the general public, keeping user data validation in the same layer as the automatic processing model is a design mistake.