I didn't notice that "extra" fabric in back in the first photos. Sure, you could pull it back when you tried, but it doesn't look like it gaps. You need a little bit of room back there to be able to sit down.
The top is loose. Wearing it untucked with your yellow rainbow skirt would look like a rumpled pile of fabric (ok, I exaggerate, but do you know what I mean?) But with fitted pants like these, I think the extra fabric is fine, as it softens the whole look. Otherwise it's all structure/body shape.
And I agree with others who say that you look awesome!