What follows is my opinion only. I would not presume to tell others what they mean when they use a term, I speak only to how I express myself.
Folks new or even relatively new to OD&D games frequently mention how the game is "rules light" and go on about how all those rules aren't needed. I agree to a point but I believe many folks are missing the basic point of how the game was intended to be used. A common theme running through Gary's writing was my oft-repeated mantra: it works the way I say it works. It isn't the idea rules are bad. No, it was rather the referee could probably come up with rules that suited his refereeing style better. The generic stuff is covered, e.g. how likely to hit a target is an arrow fired from 50 yards, or how far does a chain-clad warrior move when running? And even those rules are easily modified.
Most of us would likely feel movement adjusted per specific footwear and surface gradient to be overkill. Any good footwear on a solid surface is as far as we'd take it, but not everyone feels that way. I've made cracks, over the years, about games that play "like a spreadsheet." To me? I can't imagine anything more boring but I recognize there are folks who live for this type of fun.
As I see it OD&D to some degree was written the way it was to enable referees to pile on this sort of detail if they saw fit. A ref who loved sailing and wooden sailing ships might greatly expand the naval battle portion of his rules and center his campaign around such. If not, the typical ref had all he needed to run a pitched naval battle versus a bloodthirsty crew of miscreants and misfits.
Anyway, as one's campaign grew and expanded the ref could add on rules as needed. As they worked or were subsequently honed until they did work they were added to the "rules." So in time a campaign could, under some referees, grow to rival the complexity of AD&D itself. It all depends upon what you as referee and his gamers wanted.
I tended to cater to a more casual group of gamers so I kept my campaign light. I favored and continue to favor light-fast-easy when making a call. But, and this is an important point, I was confident in my ability to make off-the-cuff rulings. If I really liked that ruling it went into my campaign notes but if it was a rare situation I didn't even do that. I've played in other games where the ref's house-rulings were a thick notebook with dizzying (and rather intimidating) levels of detail. While I still enjoyed the game I wouldn't want my regular game to be like that.
My point? Simple out of the box doesn't have to stay simple. For every referee like myself there was at least one other who felt there simply weren't enough pole arms in the game.