They are the same length.
Look at the points of the arrows and crooks of the branches.
Nope, still different.
If you save the image as png, the tip of the leftmost arrow is at 68 pixels and the one of the rightmost one is at 393, while the crooks are 73 and 388.
I hate that the author gave a picture in which the two lines actually are of different lengths, as you can see from trying to pick a rectangular screenshot.
I'd quantify the exact feature in the line that I'm using for reference (which would be by itself ironic considering the discussion on well-defined relations between entities attached to that picture), but it's unnecessary - none of them match!