One of the problems with string mops is that you can’t mop the corners without mopping the walls.
You have to either :
Do the corners by hand with a rag or brush,
Hope your sweeping or dustmopping the edges is sufficient with no wet mopping.
Accept that there is going to be some deposit of mop water residue on the baseboards.
While we generally refer to them as microfiber mops, it is also common to refer to them as “flat mops”, and because of their flat architecture, we can now get all the way into the corners, particularly in restrooms, without staining the baseboards or tile walls. Nice side benefit of a green and highly productive technology ?