The Bug

In Minecraft 1.20.4, and likely other versions (1.20.2 only other tested version), while in spectator mode, the buttons on the crafting recipe menu do not work. Animations work, item names appear on hovering, and you are able to click the button that opens the menu; however, the menu itself cannot be interacted with.

How to Reproduce

1. Go into spectator mode
2. Enter inventory
3. Open the crafting recipe menu
4. Try to click on any buttons in the menu, none will work

Likely Explanation

I'm not a big expert in Minecraft, but I know that you are unable to interact with items in it (though some plugins make it possible). It's possible that this bug occurs because of spectator mode disabling interaction with slots, likely including the crafting menu.

Note

After searching to see if this has been reported, I have found a similar report (MC-116179), of which has been marked as resolved. Assuming this means that the bug [had] been fixed in the past, it is now either intentional or has resumed to be a bug (presumably).