Since purchasing Skylanders with my son and realizing you can't have different profiles on each character, I've also noticed some achievements are not unlocking depending on who first used the Skylander and who it is tied to. In short, all the Skylanders appears to be tied to my profile, but it's preventing some achievements from unlocking on my son's profile.
They aren't just the achievements described with (primary profile), as most have unlocked for both of us while playing separately. So far I've noticed that the following achievements won't unlock once a Skylander is tied to someone:
Fashion Stylist - Have your Skylander equip a hat for the first time. (primary profile)
Hello!! Skylander - The first time you put your Skylander on the Portal of Power. (primary profile)
What other achievements are tied to a Skylander unlocked by a specific person?