Yes, I agree, the new yield values should be communicated to the player so that crafting could be as efficient as possible - when needed.
However, F1 encyclopedia isn't a good place for this sort of information as the values are prone to change.
Written descriptions (eg. +'Slender Trunk, yields 3 arrows') at recipes would be somewhat working hack, but as the requirement dialog is displayed only after selecting the number of items to craft it would need cancelling and crafting again to correct the desired number if need be.
I'd like to have the information displayed dynamically upon crafting without requiring any additions to the diy_ recipes.
Just haven't had time to consider a good practical approach to it just yet. One solution would be to display the applicable yield information as a game message before selecting how many to craft. For example like this:
HANDCRAFT OPTIONS: Arrows
ARROWS: Blunt arrows
One slender tree trunk can yield 3 blunt arrows.HOW MANY (OF TOTAL 10)?
I think the raw material loss, be it slender tree trunks or something else, will remain a part of the crafting system in the future too but the yield value can ease it up to some extent.
In theory all the wood raw material and their requirements could made length based so that for a blunt arrow you would need "1 meter of slender tree trunk" but uh...that sort of an overhaul is pretty much out of the question at the moment as there's quite a bit of something else on the table right now.
Moreover, we like to think that slender tree trunks also differ in shape and size and sometimes you might find less good portions of wood for eg. blunt arrows from some of them.
Of course this isn't reflected in the game on other than imaginary level, but it may help to cope with the material loss if you roleplay it that way
Raw lumber one fells in the game isn't always of the same standard shape, size and straightness.
Nevertheless, the yield information upon crafting is a good and solid idea, also on our to-do list, and ideas for the implementation are welcome.