So.. Let's say you want to import a schematic, but don't want a specific block in it. You use the filter aaand it'll only remove every block associated with it like if you want some random nether brick stairs block gone, every stair block gets removed. Or you could have the ability to head into a viewport and select which specific block/s you want gone from your schematic if you're too lazy to go into the world and delete it yourself.