Basically, the honey level from the Bee Nests and Beehives Inventory icons are coded in a way, that it only updates if the Bee Nest/Beehive has honey_level 1 or 5, but ignores the level 2, 3 and 4, making resource packs that add new textures for those honey levels ignored in the inventory.

Steps to reproduce:

• Place down Beehives/Bee Nests in rows of 1x6
• Get a Debug Stick
• With the Debug Stick, change the honey level of each Beehive/Bee Nest by 1
• Break the Beehives/Bee Nests (in creative)

Expected Result
The icon for the item would display the front texture accurately based of the honey level.

Observed Result
It only displays the empty and full honey variants.

In the textures\models\item there's only 2 variants (by default) for the beehive/bee nest item models, "bee_nest_honey" and "bee_nest_empty" (or "beehive_honey" and "beehive_empty") and in the .json files, it's coded so the icons change when honey level is 0 or 5, while the other levels load the empty texture.
Some resource packs such as Vanilla Tweaks have options for more accurate bee nest/beehive honey levels and if this doesn't get fixed, similar packs will break.

In the pack below, I replicated this bug and broke the level 5 honey filled blocks. And in the screenshot with the beehive/bee nest items, they all have a different honey level (1 --> 5)