I've seen offsets and sizes with E-13 values, those don't make much sense and in some cases can make subtle differences in the corners, sizes and offsets that show lines in the fuselages and make the files harder to read.
Of course it should allow full precision for typed inputs but when using the dragging tools anything smaller than 1mm precission is just impossible and even with non-zero values in the grid size the tools can add small imperfections.