Filters being their own sensor type creates unnecessary sensor sprawl in HA configs.
Filter sensors currently have a relation ship of one source entity, it seems like it would be vastly more efficient to simply allow the “filters” attribute to be applied to all user defined entities or as customization to ALL entities that behind the scenes altered the output of the original entity. As it stands many filters just contribute to noise in the history / log book / recorder that then needs to have additional exclude entries so that data is not being recorded multiple times.
There are cases where it is useful as a separate sensor, but in that case I would argue it should be only as an attribute of a template sensor to serve the same use.