If a resource pack has the pack format number at 3, it will not be applied

The bug

If you use a resource pack made for 1.13 that has the pack_format number at 3, it will not work at all, even if the file paths are compatible with the game.

How to reproduce

1. Download and load this texture pack.
2. Get a block of granite and a golden sword.

Expected Behavior

They should use the textures from the pack, just like how it would work if you change pack_format to 4.

Observed Behavior

They're both using the default textures.