The sentence in question is in the tour. The goal of the tour is to provide a “quick overview of the site” for new users, not a complete set of rules covering every corner case¹. Therefore, it is okay if that page is not super-precise on this aspect.
I don’t think anybody will refrain from asking an on-topic question because of that line. Askers of such questions cannot know that their question might fail this criterion (if overinterpreted) because if they did, they would already know the answer to their question. Also, going by all the off-topic questions we get, many people ignore the guidance we throw at them anyway.
If anything, there is a risk of users overinterpreting that line when it comes to community moderation.
With all that being said, I would suggest to remove that point completely because it is unnecessary. I don’t think anybody who made it past the first paragraph of the tour will ask blatantly off-topic questions (e.g., about programming). Many other SE sites don’t have such a rule in their tour and they are not suffering from blatantly off-topic question any more than we do. Rather the line is disengaging on account of stating the obvious. Any complex formulation of that rule to avoid overinterpretation by community moderators would be equally off-putting and possibly misunderstood by new users.
¹ If any page is a reference on our scope, it’s this one. Interestingly, it doesn’t have any comparable rule at all and just assumes it as given – which I think is fine. Admittedly, it is quite heavy on “don’t”s and could provide some examples of things that are okay to ask, but that’s another issue.