actually, "spline" is an incorrect term for graphite rods. it applies to bamboo rods (among other non-fly things) which use slats of bamboo to construct the blank. in the graphite and fiberglass world, it's called the spine. or effective spine.
there are at least three views to the spine concept when affixing guides. two have opposing 90 degree views and the third says don't worry about it. there is NO twist because of the guide placement in relation to the spine. it's up to you to decide what you want to do of course and if you settle on one method, it's doubtful you'll notice any difference unless you develop tests on all three methods. and from what i read, you'll see there's not much difference.
most who make a big deal about it have garnered their education from long held beliefs. and those can be inaccurate. probably the most up to date info can be found here:
for what it's worth... when i started, i pulled my hair out at this beginning step and decided to wrap guides for fly rods on the effective spine. now (like several major rod companies from what i read), i simply wrap on the straightest axis.