Most blocks and items don't have shadows in deferred rendering

Steps to Reproduce:

1. Create a world with a PBR enabled resource pack and the "Render Dragon Features for Creators" experiment enabled;
2. Look at the ground and observe the shadow created by your arm (or your entire body if you're in third person view);
3. Grab any block or item.

Observed Results:
Most blocks and items don't have shadows.

Expected Results:
Every visible object has a shadow.

Screenshots/Videos attached: Yes

Notes: Some blocks such as trapdoors and leaves and item attachables are unaffected by this issue.