If a filter is set to "Maintain Counts", it can place more than the count has.
For example, if you have a netherite puller providing scaffolding to a chest, and have 12 items in the filter- it will deposit 16 into the chest.

I think it does this because the netherite puller grabs groups of items and dumps it's entire payload.

If you decide to leave this bug, people can use a slower puller if they want better accuracy (which would make real world sense).
:) Just thought I'd bring this bug to your attention.

Good catch. Will look into this 👍