A little testy are we? I think its ok to raise the opinion that it looks odd being able to see from outside the land. Sure its a theme park, but with the mentality of "theres only so much we can do" much of Diagon Alley and all the cool things in it wouldnt exist in their current form would they? Its about suspension of disbelief, and since Universal wants guests to buy into the fact that its real I think its ok to want things to be as real as possible and true to their stories.
That being said, I dont think it matters so long as in the actual London area you cant see it...thats where the "story" takes place, so as long as everything inside the actual land is hidden it should still 'work'