Yes to some degree; simply because it is the river and environmental conditions that determine how we can best approach our target areas. And that narrows our choice, if we want to fish efficiently.Are we not in effect, honing our casting skills every time we go fishing...?
As in, we dont get to use a single-spey off our our preferred shoulder in every circumstance.
For me, that is part of the fun, wheras, some will cross to the otherside, or station themselves in a less than ideal spot - as they don't want to spend their day getting tangled, or ducking from the fly, or being unable to cover the fishable distance - simply because their casting ability is limited to one basic cast.
I know I have said it a million times, practice, practice, practice.
To those who think practice is a waste of time, I say poppy-cock!
Another reality is, that some folks will never become highly skilled, no matter how much they try. Its a simple fact, and there is no fix; not even reading an understanding thread...