I can clarify this. This particular aspect of skill bonuses is a bit fiddly to avoid making it advantageous to simply craft something with all Q1 reagents, and then recraft it with all Q3 and get full skill when doing so. If that worked, we would often do that, as the recraft takes somewhere around 40% of the reagents in the original craft…yes it also takes Artisan’s Mettle, but not much.
So the way this works is the item “remembers” the quality of the reagents you crafted with. Let’s say the original item can give you 100 skill from reagents. In this world, if you craft with all Q3, you get +100 skill. If you craft with all Q2 you’d get +50 skill, and all Q1 and you’d get 0 skill.
Let’s say you craft the item with all q1 reagents. You got 0 skill.
Now if you recraft using all q3 reagents, you’ll get +40 skill. It’s effectively “replaced” 40% of the old q1 reagents with q3. Recraft again with q3 and it’ll go up to +80 skill…you’ve replaced another 40%, meaning you are at 80% q3, 20% q1. Finally do it a last time, and you’ll get 100% bonus skill again, +100 skill in this case. It works in the opposite way as well. If you recraft with lower quality reagents again, you will replace some of the best reagents with bad ones again.
So in this case if you crafted originally with all q3, you’d be getting +100. If you recraft with q1, you’d replace 40% of those with q1’s, so you’d get +60 skill. But luckily if you recraft again with Q1, it’ll just replace the old Q1, so you’d stay at +60 skill. If you then recrafted with Q3 again, you’d go back to +100 again.
Here’s a picture example:
Initial craft with all q1 (+0 skill from reagents):
First recraft with all q3 (+40 skill from reagents):
Second recraft with q3 (+80 skill from reagents):
Final recraft with all q3 (+100 skill from reagents):
Hopefully that helps clear things up!