Essentially, as it is right now you have to carefully size parts so that their materials match up (or use CSG). This ‘global property’ would make it so materials on anchored parts are world-aligned and their materials will line up even if they are at different positions/sizes. This is useful for ‘showcase’ builds as they get to have materials which line up, like they probably would IRL. This makes games more immersive.
As for the property, it would probably be a boolean in Lighting. I can’t come up with a name which would accurately describe this without being convoluted though.