Alpha Opacity items make NBT blocks invisible when item is dropped in front of NBT block.

Much like the title says:

Items with Alpha Opacity (Semi-transparent. Like Stained Glass Blocks/Panes, Slime Blocks, Ice etc.) Make placed down NBT tag-able blocks (Like Chests, Beds, Shulker Boxes, Signs etc.) invisible when Item is dropped in front of given NBT tag-able block. Creating a see-through like hole.

The same issue does not apply with Leaves, Non-Stained Glass or Iron Bars etc. Since they are fully transparent and not semi-transparent.