The custom close reasons are custom, off-topic reasons, and most sites already list them on the /help/on-topic page. For Ask Different, this is true: "Please refrain from asking about the following topics as questions with these core subjects are generally closed or deleted..."
If you'd like the wording to match exactly, that on-topic page is moderator editable. Just edit it to use the same language as the custom close reason. The /help/dont-ask page is more about the style of questions that are universally not a good fit for the Stack Exchange model. Some sites – for example, those that explicitly do not allow shopping recommendations, or those that explicitly do allow them – might have some overlap between the /help/on-topic and /help/dont-ask pages, but I'm not sure that the latter needs to be customized to match the close reasons.