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: