Not sure if this is intended or not.

When using the "Crafting recipe tree" feature, items in the offhand are not considered in the "synthetic favorites".

Items (stripped logs) in inventory:

items (stripped logs) in off-hand:

Version: v1.1.18+1.20.1+fabric

While this is not ideal this is EMI working as best it can, the offhand is not directly available for in basically every crafting screen so it's not considered "available".