It all comes down to the definition of property. I'm going off of memory at this moment as i'm getting ready to leave....but yes, once upon a time i would have agreed with you that mixed-use was only employed on individual structures....but there has been clarification now (i'm fairly certain...again, don't really have the time to look it up at the moment) that "property" doesn't refer just to ONE structure, but ALL structures on one property. At this moment, i'm struggling to remember where to look for this adjustment to the meaning of "property", but i'm fairly certain that that meaning has indeed been clarified. If no one shows up with a better answer to my rambling one, i'll attempt again tomorrow hopefully.
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I'm fixin' to fix that.