I’ll grant I’m much more inclined to the “book” side of gamebook. But I don’t think it has to be black or white. After all, even video games let you choose the difficulty level. Yes, it’s a design choice and they are all valid. Personally I prefere a story centered game than a skill centered game.
That’s a good piece of advice.
If I somehow beat the minotaur with a chance of 10%, you could add the text that even you (the MC) doesn’t know how, or something like that. Makes the player aware that there’s a distinction on winning by skill and winning by luck.
Generally, and iirc it’s part of CoG’s guideline for their choice of games, when you do a skill check you don’t increase the same skill. This is to avoid a feedback-loop. So choices are broken into “training” (when a choice increases the skill) and “testing” (when a skill is checked in a win/loose dynamic). By the way, those are just how I call them, nothing official, 
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With your system you could have a skill increase if the player wins by luck, which feels realistic while avoiding the reinforcement feedback-loop. It encourages exploring other choices even late in the game because I still have a chance, albeit smaller. It adds a safety net and minimizes frustration… Thinking about it, it should just be standard practice.