Partially transparent blocks don't cast shadows when held (Deferred Technical Preview)

Steps to Reproduce:

1. Create a world with a PBR enabled resource pack and the "Render Dragon Features for Creators" experiment enabled;
2. Switch to third person view (first person is affected by a different issue, see MCPE-178456);
3. Look at the ground and observe your shadow;
4. Grab any of the following blocks:

• All colors of glass
• All colors of glass panes
• Slime block
• Honey block
• Beacon
• Ice

The only thing all of these blocks share in common is the use of a material that supports partial opacity. Even the uncolored glass and beacon, which don't appear to fall into that group at a first glance.

Observed Results:
These blocks don't cast shadows at all.

Expected Results:
All of these blocks cast shadows.

Notes: