Thank you for this mod! Really cool!
Using latest forge 14.21.1.2387 and JEI 1.12-4.7.0.68, I can't find wearable backpack in recipe list in survival mode. Strangely enough, I can see it in creative and pressing R for recipe shows the recipe! I can even make it in survival, just not visible in JEI.

Apologies, my mistake, all good and visible in JEI, it was texture interference from another mod.

No problem at all. If you do find any issues, let me know. I haven't had much chance to test WB for 1.12.