While it is possible to turn some existing girth into length, it is very unlikely and the amount would be very small with a normal Penis Enlargement routine. I think if one wanted to do this it it would have to be done very gently to avoid injury therefore taking a long time to reform the penis as is commonly done with masturbation. So, basically it is irrelevant.
Furthermore, I gather it is currently believed that it's impossible to specifically target one dimension rather, that everyone gains differently. Though it is also likely that numerous variations, such as technique or bio-available nutrients, can alone cause 2 people to gain differently from the same exercise.