One boat keeps clear of another if the other can sail her course with no need to take avoiding action and when the boats are overlapped on the same tack, if the leeward boat can change course in both directions without immediately making contact with the windward boat.
Excellent, you have finally understood.
The immediately is the critical thing here, you are far enough apart that the contact will not be instant, so giving the other boat time to avoid.
QED.
