It's unfortunate that the Optional Relief rule is under the title "Relief from Obstacles".
However the starting phrase for the Optional Relief rule says: "A player may elect at any time to take optional relief..." which means that it does not need to be relief from an obstacle.
I acknowledge that and that your interpretation is not unreasonable. But context seems kind of important. What is to prevent the following from allowing a player to throw from out of bounds:
"The lie may then be relocated by marking a new lie which is farther from the target and is on the line of play."
This would seem to be an absurd result which would seem to mean that there are some limits to the relief rules.
Also, when I look at 801.01, I see a familiar principle of applying the most direct rule. Which is more direct, the rule that tells a player to play from a lie within one meter of where a disc went out of bounds or a relief-from-obstacles rule that allows placement at any point on the line of play further from that lie even when there is no obstacle?
Finally, with a little further looking around, I see that another hint about the "optional relief" rule and its "free relief" description when associated with an OB situation from the definition of a penalty at 802.01(C).
"Penalties that are associated with making a throw are those for: out-of-bounds, hazard, missed mandatory, above two meters, stance, marking,
taking improper relief, and lost disc."
This seems to suggest that when improper relief is taken, that is, relief that is beyond the relief from an obstacle allowed by 803.02(A) and (B), that you get a penalty, which would mean that the word "optional" doesn't necessarily mean that the relief is available in the absence of an obstacle, but rather the option is that if there is an obstacle, more relief than is available without penalty (i.e., "improper relief") may be taken with a penalty unless the disc went out of bounds.
Your offered interpretation of 803.02(E) would, along with the "improper relief" comment from 803.02(E) seem to imply that 803.02(C) allows the player to basically, walk from the obstructed lie to the basket, drop down a mini, drop in the his putter and add one penalty stroke. This could potentially allow a player on a Par 5 to throw to a spot behind an obstruction (1 throw), walk to the basket, put down their mini, drop in the putt (1 penalty throw for improper relief and 1 throw) and card an eagle 3 on the hole. Because if "relief" is not "relief from an obstacle" limited to "too far back along the line of play," then that one penalty throw would govern that hypothetical unless I am missing something.
While not strictly reliant on the language of the rule, it does seem to make sense to me that if a dangerous insect, animal or people are present near OB, you might want to let the disc golfer get as far away as they need to feel safe about not hitting them with an errant throw and not limit them to enough room to clear the danger - just as one example of why no penalty would be assessed if the OB rule mandated lie were behind an Obstacle as defined in 803.02(A). That would be my take on the application of fairness to this rule as mandated by 801.01.
And that location of the rule in the obstacles and relief rule does seem to give further context even if that context is "unfortunate" to a wider interpretation.
Again, I'm not saying your take is unreasonable. It just doesn't seem as clear to me as you seem to think it is. A reference to 806.02(D) to 803.02(E) would help to make it clear that your interpretation is, indeed correct. A change in language to 803.02(E) could help make it clear that it is not a "free relief from OB" if that was not intended.
As to Chuck's "ground-already-covered" rule, I really kind of hate that as someone who has left some pretty thick rough on a few courses. If the player wants a do-over, they should go back to the previous lie with a penalty, not anywhere in between that lie and their new lie. Just my opinion.
BTW, this is all hitting me as I think more about this rule after a long day of (mostly) working on writing something very long and complicated, so I acknowledge that I may be missing something obvious. Feel free to pull the rug out from under my reasoning.