it is a well-known feature since the beginning of w5 with bark boats, or the system itself is well-known since i started playing, thus
my parody to tell people to put birch bark first(or at least before normal bark) in your inventory. a birch bark is also regarded as a bark, and whatever you interacted last will be used first on this game system.
= example =
you pick up 2 birch barks, 2 normal barks, 2 branches and 2 strings -> 2 boats
you pick up 2 normal barks, 2 birch barks, 2 branches and 2 strings -> 1 boat and 2 normal barks, a branch + a string left
same thing happens when crafting hardened leather
you have many leathers and wax in your inventory and make a hardened leather, newly made hardened leather will be counted as a normal leather, so it will be used as a leather when you make 2nd hardened leather if you keep on without interacting with other leathers or removing the crafted hardened from your inventory.
or, with cone cows / branches and boughs
you pick 2 cones, 7 branches, 5 boughs -> 2 cone cows and 4 branches left
you pick 2 cones, 5 boughs, 7 branches -> 2 cone cows and 4 boughs left