The reason that reloading is banned in XOTM and HoF, at least to my knowledge, is that it makes games less comparable and allows for ridiculous "luck manipulation".
I am firmly against the perception that XML knowledge is cheating. It's as you said ---> these are things that can be picked up via playing the game enough times. At that point, why would someone avoid important knowledge or delay their attainment of it?
In normal play, IMO reloading isn't really frowned upon unless it's "overused", which will vary by person how much qualifies.
In my case, I will save the game at major decision points, and if I lose I come back to them and try another decision...at which point I admit to myself (and the forum, if it's a forum game) that I lost and why, and the new approach I'm taking. The only other times I reload are flagrant game input errors: I click on a leader's name without a damned finger anywhere near the keyboard, and it declares war. On my DP ally (or anyone). That kind of stuff I'll reload...thank god it's yet to happen when attempting BOTM.
But just knowing the game mechanics? No way is that cheating, anymore than reading an instruction manual is cheating.