Well, when? RPGs invite house-ruling more than board games. At the very least, board game house rules tend to be stated upfront, perhaps with somewhat more clarity and directness, as they change one or two things, where an RPG GM’s interpretation of the rules as written can be substantially looser.
Often when playing a game, someone in the group takes the role of resident guru. They may own the copy being used. They may simply be the most well-versed in it. They may be the GM, if the game calls for such a thing, such as most role-playing games. At any rate, they get a certain amount of deference when it comes to interpreting and remembering rules. This guru, though, is not always the game host, the person who owns the copy or did the legwork of getting everyone around the table.
This situation happened to me over the summer, playing Arkham Horror at a friend’s house. He’d invited folks over for an afternoon’s game. As the raving Arkham Horror fanatic, I found myself often teetering on the edge of uncertainty in the course of play: should I mention that technically, a rule worked one way, rather than the other, or not worry about it?
In that instance, I think I corrected more than I let it go, which doesn’t say much for my ability to lean back and not worry about the rules as written — at least when it comes to board games. In role-playing games, I manage to be much more laissez-faire, particularly when GMing.
At the role-playing table, it’s at least a social faux pas and more likely an astonishing breach of courtesy to quibble with how the GM interprets the rules. Or I think so. I’ve been in a few groups where interpreting rules is a god-given right to anyone who plays. And honestly, listening to the back and forth gets downright miserable. Take for instance one table discussion I sat through about Raise Dead versus Resurrect in Dungeons & Dragons. None of the characters at the table could cast either of those spells, but the bickering over what they could do went on for forty-five minutes.
So role-playing games are a situation where I’m almost always going to defer to the GM’s interpretation, simply because they’re so prone to house rules and modifications that arguing for “rules as written” is wasted time, taken away from playing. Even in board games, though, I try to defer to whoever owns the game or proposed they play it; usually because they know it best, but also for expediency’s sake. I’d rather just play the game than quibble fine points of proper play. During the game, that is. After the game ends is the appropriate time to debate those questions of rules interpretation and, when feasible, look up any online errata that may exist.