No, you are not missing anything. For swimlane columns and rows, there is indeed no width/height/size property. Currently, columns and rows can only be re-sized one at a time by dragging their borders using the mouse.
Currently, the only way to get a column or row of an exact, specific size is to set the table node's "Default Column Width"/"Default Row Height" before creating a new column/row using the table node's context menu.