I'm self-assigning this one. The solution won't be perfect, but it will be better than how it currently works.
Currently, it only works for recipes that are ShapedRecipes.class, ShapelessRecipes.class, ShapedOreRecipe.class, and ShapelessOreRecipe.class. Looks to me like this could be replaced with instanceof checks and not break anything existing, and allow extensions of those classes to work without a custom PageJsonRecipe, which can't have a renderer passed to the constructor.