When the enchantment glint is applied on some items in the GUI or entity models, it seems to be impacting frame rate times when a certain number of them are being rendered. This is more noticeable when a large number of enchanted items or entities with enchanted armor show on the screen. Compared to when the glint is not applied, rendering it when it's present ends up being more intensive.

Do note that these tests were made in low end hardware, so the result might not be really apparent outside this instance. Some of these results could be also caused by MC-166101, due to how the enchant glint renders multiple times when an item has multiple layers (such as leather armor, etc).

Some of the screenshots were taken on fabric, but can be reproduced in vanilla as well.

How to reproduce

1. Create a void world.
2. Place both a double chest of golden apples and another chest of enchanted golden apples.
3. Open both chests and compare the frame rate.
4. Alternatively, compare the frame rate when looking at a row of armor stands with enchanted and unenchanted armor (as seen in the attachments).