I think it depends on how you define "getting anxious over tasks you know they can do perfectly well." You use the example of getting dressed. DS definitely doesn't get anxious over whether he can dress, but during high-anxiety periods he frequently looks like he's having a panic attack while he's getting dressed because he's concerned if he doesn't dress fast enough he might miss the bus, even though we have 10 or 15 minutes before we are leaving the house.
BTW, DS is definitely a perfectionist -- of the variety that would rather not attempt something if he isn't sure he'll excel at it. For example, when we had him tested this summer, the psychologist noted that DS would say, "That's too hard. I can't do it." But when told to just try and do his best, he was able to do that problem and several more difficult ones that followed.
DS can tolerate some change to routine, but it depends on what the change is, how anxious he is about life in general at that time, and how strong his vision of what's "supposed to happen" is.
