That's my point. Imho it's impossible to even come close to a realistic chance to beat this game without knowing more or less every detail of its internal mechanics. And you can't infer this knowledge just from playing. You need to look it up from some out-of-band source.

So only letting an AI play this game will not reveal anything about the "reasoning" capabilities of said AI.

Letting the AI read the source (or some other "spoilers") and than look at how it performs playing would be maybe a usable test. But that's still a big "Maybe" imho as Nethack is just "too random" I think.