Wherever two edges contact or intersect each other, the portion between contact points is considered a separate edge from any other portions that might happen to be colinear with the segment in question. This is the nature of SketchUp. For example, if you draw a horizontal line and then draw a vertical line across the middle of the horizontal line (to form a + shape), the result will be four edges: two horizontal and two vertical, separated by the intersection.
The separation across intersections can be avoided if the horizontal and vertical edges (in my example) are in different contexts - different components say. Then the intersection will be purely visual and it will not divide the long edges into multiple shorter ones. Depending on one’s goals, that approach might be useful or might not.