Given the wide disparity between the sorts of activities given as examples of Light Activity and the sorts of examples given of Strenuous Activity, I don't see it as quibbling. If I wanted rests to effectively only be six hours, I'd just change the length of the rest outright rather than keeping it at eight hours and allowing up to two hours of adventuring activity.So my question is - for the rest of the time is it really worth quibbling over whether an activity is light or strenuous, and runs for an hour or for two hours!? Why not just rule it like this -
A character gets the benefits of a long rest at the end of any 8 hour period in which they had positive hit points and slept 6 hours. They can't get that benefit again for 16 hours.
And allowing Strenuous Activity to count towards a rest encourages things like planning overland travel in the middle of a rest period, which is the sort of contradiction in terms I want to avoid. I want rests to feel natural, rather than be something to be gamed.
I am fine with shortening the minimum time before a character can benefit from a second short rest to something like 20 hours, to permit the party to rest once per night with some late nights and some early nights. The 24-hour-rule creates a one-way ratchet where going to bed late one night means every subsequent night has to be just as late until you skip a long rest to reset the timer.
I disagree with your interpretation that RAI counts time spent on Strenuous Activity towards the minimum downtime requirement. So your question seems moot to me.I think you overlook the main point. I'll try to reframe it. Given I feel it is okay to have an hour of adventuring while resting (RAI) why on Earth should I object to two hours? What is more credulity stretching about two, that wasn't already stretched at one? And given that RAI makes rests essentially non-interruptable, only extendable as you (more-or-less) previously observed, even less reason to worry about what happens in that two hours. Players can just roll the rest forward.
Do you follow? Under the RAI, the only part of rests worth tracking is the 6 hours sleep.
That said, if you are allowing any Strenuous Activity to count towards minimum downtime requirements, I'd say the more you allow the more credulity-stretching it becomes.