The blocking animation from shields and items with the blocks_attacks component is not reflected by the block_delay_seconds field. As a result, blocking with a shield with a high block delay is not visually different from a default shield, or a shield with 0 delay.

This may or not be considered a valid issue, however this makes it difficult to guess at what time the item is supposed to start blocking as there's not enough visual feedback. It's also worth pointing out that the eating animation on items with the consumable component is already reflected by the consume_seconds field, being slower at high values and faster at slower values.

How to reproduce

1. Give yourself a shield.
2. Now give yourself this custom shield:

   /give @s minecraft:shield[minecraft:blocks_attacks={block_delay_seconds:3}]
   

3. Compare both blocking animations.

Expected result
The blocking animation would be slower on the custom shield, raising up until the delay seconds have passed.

Observed result
The blocking animation is the same for both shields, despite one of them taking 3 seconds to start blocking attacks.