Well, here's the thing, in my opinion: Projects don't really exist.
I mean, sure, they exist as an organizing tool. But a project just consists of actions and reference, more or less.
The value in a NA list is in its completeness, so I'd be hesitant to start leaving things off of them just because I've already got some NAs from the same 'project'.
Does this make the lists bigger? Sure. Making a list more complete is always going to make it bigger.
All that being said, different people are going to implement different systems that work best for them. If you want to defer some NAs based on project, the GTD Police won't be coming after you.