He's referring to what I said.
1. A single user can have dozens of filters each with the same tags in them; we would have to make a single "filter" for each user that has all tags, else the count is inflated
2. Many users just use complex filters instead of simple filters; parsing these into a simple "this tag is filtered" would be a serious undertaking
- they can be there as as simple exclusion, like in a simple filter
- they can be there with conditional exceptions (tagB unless with tagA)
- they can be the exception itself you never want filtered
- they can be used as a global exception (an always-on search)
- they can be using a term that's aliased (eg. tx instead of trixie)
3. As a lesser / more pedantic issue, people often filter a parent tag that implies the actual tag they want to filter, ie. filtering all of "grotesque" when you just wanted to filter "scat"
4. Similarly, a lot of people are perfectly content using one of the default filters, or a shared public filter; do the tags in those filters also count per use?