I don't think the alchemical formulas are in black and white.

I know for sure that the lower level bows don't require the grass as a mandatory second element.

I also noticed that if using primary one ever adds wood+grass you are almost guaranteed a bow instead of a pure wood product. The tilt is AT LEAST 80%.

That being said, Primary alchemy has an "instability" factor that has been noted on many a forum post on the main website. This instability factor actually makes it MORE desirable for making certain compounds since there is the odd chance of getting something good that was unexpected. Might spend more money, but might also pick up a crazy item that is otherwise unachievable without Superior+Book(expensive with a failure rating).

So, I think checking confirmation is important, but since bows are limited to below rank 14 and we pretty much KNOW how to get a bow, I don't think its a major concern. I would leave the flags up, anyhoo, just to make sure the noobs don't forget the general rule of thumb.