Why is ITransformFactory.Build called when ITransformFactory.Validate returned false?

[Ghostbird]

What I would have expected is that it worked something like this pseudo-csharp:

// Build route transform usage information based on validation
var routeTransforms = routes
  .SelectMany((route) => route.Transforms
    .Select(transform => transformFactories
      .Where(factory => factory.Validate(new(route), transform.Values))
      .Select(factory => (route, factory, transform.Values))
    )
  );
// Build route transforms
routeTransforms.ForEach((route, factory, values) => factory.Build(new(route), values));

However instead the same progressive iteration is used for both Validate and Build. Which means that Build is called a lot with data that's not valid. Which means that each Build implementation has to reimplement the entirety of the Validate method. Which means that Validate might as well not be implemented and just return true.

Why is this so weird? Or do I fundamentally misunderstand something about how to use the transform factories?