I am often quite critical of USTA for the way they run the open - 3 day round 1, squashed up end of tournament and Monday finish etc but in their defence they are always very proud of their defending champions and also think they have always liked Andy as he is such an open fan of their event so I don't think they are putting him on Wednesday as a snub . It means they anticipate having him on Friday and Sunday which will be prime time viewing over the labor day holiday weekend. Also they are spreading Fed Rafa Djokovic and Andy to give them big names over first three days. And notice Fed and Rafa share day one billing (granted over day and night session), Djokovic and Andy get their own day each.
the trouble with this theory ww is that labor day is the monday so prime time viewing would mean Andy playing sat and mon, though at present it's not at all clear which day he will be starting it seems.