If you're burning weed in an enclosed space, you're simply going to get a little high. There's no getting around it. They would have noticed this at some point, and made a decision to either move forward with using it or keep it away.

Apparently they decided to keep moving forward with it for some period. This isn't some sort of tacit "pro weed" observation. You're more than welcome to say that they were wrong for using such a thing (either for such a purpose or while ignoring those effects), but the basic investigation still remains. They were burning it and they kept burning it for quite a long time, and there's simply no getting around feeling the effects if you're burning it like that (albeit to a much weaker degree than someone who is inhaling it straight from a bong or whatever of course)