It took me a while to comprehend this length theory, until I found out that a liquid IS IN FACT COMPRESSIBLE.
It seems that the fallacy that liquid is supposedly NOT compressible is more prevalent than it should be.
Here's a chart that indicates that liquids are in fact compressible:
http://hyperphysics.phy-astr.gsu.edu/hbase/tables/compress.html
Mark.
It's my understanding the lines themselves aren't solid either (ref piezo tach sensors for example).
The ballooning of the lines as well as different length lines subtly alters the injection event profile.