Spline finding is above all a stability issue, where the rod will be stable
under load. With the guides on the bottom of a fly rod and the reel there
also, stability would seem not to be an issue.
Sage, Loomis, etc do not spline their rods, they put their guides on in
such a way as the hide any curve in the blank with the guide placement.
They know that most rods are looked at from the top or the bottom, not from
the side where you'd notice a blank curve.
There is no sloppy, soft side of a blank. If there was we'd all be in
trouble as the soft and hard sides of a blank's spline are rarely 180 deg.
apart.