The on-topic help page and corresponding off-topic help page are pretty vague, lacking a lot of specific things that would cause their question to be closed as off-topic.
That's in direct contrast to the actual "close as off-topic" dialog we get actual, specific reasons that users never get to see:
If a user had an implementation question and they weren't sure if it was on-topic for this site, they wouldn't find anything nearly as explicit in the help as the text we see (the word "implementation" doesn't appear anywhere in the help pages), so there's a good chance the first time they find out that it's explicitly off-topic is when their issue gets closed as such.
Similarly, site reviews are called out specifically here, but they're not really listed on the off-topic page.
Ideally, the entire content of each of these points would be copied to the off-topic help page at least.