A diecast is a model, plain and simple. A diecast that you buy already built is not a kit, but it definitely is a model.
A lot of people buy built-up diecasts, take them apart, customize them, detail the, etc. How is the result of that process not a legitimate model?
I agree that posting photos of a built-up diecast and claiming that you built is is wrong. But there's no way I agree that diecasts are not models, because they obviously are.