The bug

The way the enchantment glint looks is completely dependent on how large the blocks atlas currently is. If, through use of high-resolution textures or resource packs which introduce a lot more textures, the atlas size expands, then the enchantment glint will end up looking much different.

How to reproduce

1. /give @s minecraft:nether_star[minecraft:item_model=lime_concrete]

2. Observe the enchantment glint
3. Apply the attached "enormous atlas" resource pack
4. Observe the glint now
5. Remove that resource pack, and apply the "unload every atlas" resource pack
6. Exit the world, close the game and then start the game again and load back into the world (this is required due to the continued existence of MC-263119)
7. Observe the enchantment glint once more

Expected results

In all three cases, the enchantment glint would look much the same.

Actual results

It looks much different each time.