No, the best way of signalling the design intent that you’re permanently locked in to every click you make would be to always save the latest state as and when a click occurs. We can speculate as to why that didn’t happen, of course - lack of time, unwillingness to lock the player into an unfair fail state if a bug occurred, etc. but this decision was still made at some point (and continues to be made).
But no matter how this came about, or why, I just don’t see how the implementation as-is does anything other than to segregate the playerbase into those that know about this ‘feature’ and those who do not.
I think you’re still missing what I’m getting at with making it optional. I mean, in no uncertain terms, that you should ask the player at the start of the campaign: do you want undo turn? If so, how many? Like how XCOM has ironman as an option, or how Invisible Inc. lets you configure pretty much every aspect of it (oh Klei, why can’t they all be as perfect as you?). You can literally even tell people in plain language next to the droppy-down: the design intent is that you get 1 use per battle. Or no uses. Whatever.
Basically; provide a guide to where the fun lies, but don’t dictate it. You don’t know what people have got going on. I can’t imagine how awkward it is for people with certain disabilities to play some of these things without any sorta safety net (my guess is: they don’t).
Your core argument here is everyone will pick the cheesiest option and just abuse the living daylights out of it is fundamentally flawed. If it were true, nobody would ever pick anything other than the easiest difficulty modes in any game as, arguably, hard mode is just sub-optimal play when the goal is to reach the end as quickly and unhindered as possible.
People want a challenge, have a bit more faith in them that they can define that on their own terms. Some are idiots unable to escape the morass of their own laziness, sure, but even they can learn a valuable lesson (eventually) on the dangers of cheese.