This seems backwards to me. You can have as much steer tube as you want sticking out of the head tube regardless of how tall it is. But on the larger frame the top tube will be longer, which will tend to lean you over more.The bigger bike will have a longer headtube that would allow for higher bar position.
Any Creo you buy will have the steer tube already sized to fit the bike and the bike's headtube and the only adjust you can make is with three 5mm headset spacers. Either you include 1-3 of those spacers or you don't. I guarantee if you buy an XL the fork steerer will be longer than it would be on an L...and the bars will be higher on the XL than the L. And yes the top tube on an XL will be longer than on an L but you can compensate for the longer top tube by moving saddle forward and/or using a shorter stem.This seems backwards to me. You can have as much steer tube as you want sticking out of the head tube regardless of how tall it is. But on the larger frame the top tube will be longer, which will tend to lean you over more.
(Of course the bike will come with the steer tube cut down already so you will probably be limited to stem changes unless you replace the fork)