First, glass (any type) in your hand has only the 3 front faces visible (same if you place it down).

but all the 6 faces are visible if you see it from 3rd person.

Also, there are (half) transparent blocks (in hand and in 3rd person) and particles that go under the layer of (half) transparent blocks and water that are there on the ground (see images) when you overlap them.

Holding (half) transparent items in 3rd person lets you see through (half) transparent blocks and water on the ground.

(half) Transparent blocks:

• Slime Blocks
• Ice
• Stained glass

(half) Transparent Items:

• Stained glass panes

Only some particles do that. Flame doesn't seem to do that