When applying filters such as the Mean filter, empty tiles are not densified. This prevents neighbouring data from bleeding in properly, creating surprising staircasing artifacts.

At a minimum, algorithms that cannot support sparse tiles should be clearly commented as such, and help for exposed nodes reflect this. The ideal situation is for these to auto-densify any tiles they need to touch. (A full densify isn't needed, as for example an extant of sparse 0's will not be affected by a blur, only those adjacent to dense tiles.)

Attached shows in Houdini a VDB Smooth creating distinct artifacts where it doesn't blur into active but sparse tiles. A volumewrangle upstream can optionally densify the tiles causing it to act like the Volume Blur does with Houdini volumes.