This always struck me as a bit odd since in some respects Pathfinder exists as a way to spit in WoTC's eye for creating 4e.
Notably this seems to have changed over time: In the ARG the tiefling depicted looks much like a 3.5 tiefling, he's a human with a horn. If he wore a hat no one would even know he didn't get his bonus feat at level 1.
But in later publications, notably Bastards of Erebus since that contains many of the tiefling's ARFs the race is depicted much less subtly: Crimson skin, huge tails, giant horns, sometimes even wings or hooves too, bringing them much closer to 4e's significantly more monstrous version of the race, for better or for worse (generally I see this argued either as "Yay, less 'human with something stuck on' races" vs "Boo, monstrous b~$$%*%& to appeal to angsty teens", so pick your poison).
I've just always found that evolution a bit curious.