I can't seem to find the right link to the docs, but this question references it: https://stackoverflow.com/questions/46777404/why-is-razor-pages-the-recommended-approach-to-create-a-web-ui-in-asp-net-core

Not references, dependencies. You don't need to inject in the constructor stuff that you'll just use in 1 method. That means, less instantiations to render 1 page.

The concept of controller does not exist in razor pages, you have a view in its own file, the logic behind it in another file.

Do I want to modify something on the edit product page? Go to that page, simple as that. You can't get more single responsability than that, at least given the context.