When getting a shield with the command /give @p shield[use_cooldown={seconds:0.05}] 1 the cooldown on disbale does not change to 1 tick and remains at 5 seconds. Additionally the cooldown value cannot be set to 0 or disable another way.
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cooldown on disable is modified by disable_cooldown_scale in blocks_attacks component. You should use /give @s shield[minecraft:blocks_attacks={disable_cooldown_scale:0}] instead.
I do not believe
use_cooldownis intended to affect the time the shield is disabled for. If there is a bug is that the shield is not placed on cooldown after it is lowered, as the spyglass is (unless you switch away from it, which is another bug). Nevertheless I can reproduce this so I will confirm and retitle the issue.