Probably not an intended use for most people but a little buggy all the same - if you try to print a model with zero outlines, the part actually shrinks by one line width - it's like the slicer plans the infill with a single virtual outer wall there.
Easily seen if you have a brim on - there's a single line width gap where it's leaving room for one outer wall (which isn't actually being printed).
FWIW, because I don't believe they're actually gonna update this software any time this decade, if this is something that affects you and your part isn't too high tolerance, you can sort-of jerry-rig it by setting your extrusion width to like 0.05-0.1mm and then multiply your infill size right up to get back to the right size for your nozzle. But it screws up your brims, etc.