Not necessarily. Maybe the Kelvans used images from intercepted Starfleet subspace transmissions as guidelines for their own disguises.Of course, it wasn't just "Starfleet." Heck, it wasn't even just "The Federation." You can see that even the Kelvans (well except Kelinda) in "By Any Other Name" had pointy sideburns.
(You can even see where actor Robert Fortier's actual sideburns stop and the pointy part of the sideburns were simply applied with make-up.)
So, rather than giving all the Starfleet folks pointy sideburns in common, I think it was more of a shorthand way of conveying "The Hairstyle of The Future"--for everybody--not just Starfleet. You can tell it's The Future because they have sideburns unlike anything we currently have on Earth.
Have we seen any other civilians on TOS with the pointed sideburns? And, actually, even if we have, it doesn't really tell us much (unless, of course, they all have them!). I regularly see civilians IRL wearing a high-and-tight cut, but I think the style is still generally considered a military cut.
There aren't a lot of Federation civilians that we saw. But I know that Dr. Coleman, Larry Marvick, Nilz Barris, Cyrano Jones, the Trouble with Tribbles barkeeper-guy, Arne Darvin, George Samuel Kirk, Simon Van Gelder, Samuel T. Cogley, and Commissioner Ferris all had pointed sideburns.
