ARCA stopped displaying odd-lots in their book feed a year or two ago. They are effectively hidden when routed there. Because IB uses the top-of-book quotes from the ECNs, you will not see your sell order for 90 @ 50.31 change the 50.32 offer, regardless of which market you look at or to which market the order is routed.
I have observed, in just the past few days, ARCA's streaming bookfeed, the one which incorporates INET's book and combines it with ARCA's, and this streaming bookfeed does display odd-lots, at least those resting on INET. Maybe it doesn't display odd lots resting on ARCA, but I would be surprised by such a differential treatment. I will take another look tomorrow, when the markets open.
I checked the ARCA book this morning, soon after the open. I am talking about the streaming book which includes both INET and ARCA. It definitely shows odd-lot limit orders resting on the ARCA book, as well as the INET book. It is easy to see this, because the total amount of shares quoted, at any level of the book, for either INET or ARCA, is usually a round lot number, but is sometimes not a round lot number (not a multiple of 100).
You are seeing mixed-lots (i.e. >100 shares, but not increments of 100 shares), not odd-lots. Just to be sure, I tested it with actual orders for both Naz and listed. Even if you join an existing round-lot bid/offer with your own odd-lot, the quote does not change. If your round-lot order gets hit and reduced to less than 100 shares, it will also disappear from the book. Odd-lots are completely invisible. The INET quotes are whatever INET's book feed provides, including odd-lots.
I tried the same test with SPY, and I got the same results as you. It is very surprising to me that the ARCA book treats INET orders different from ARCA orders, and that it treats the odd-lot portion of a mixed-lot differently from a simple odd-lot. I suspect that this is a bug, rather than a deliberate decision on the part of ARCA. I think it makes sense that this could be a bug. I don't think it would make any sense for them to want to do things this way deliberately.
You cant even enter an odd lot order on ARCA using IB, as I suggested. This may or may not be an IB only issue.
No odd-lots on ARCA is IB-specific. They don't want to pay the ridiculous $0.03/share (understandably). It's not surprising Jim. ARCA simply gets the same book feed from INET that everyone else does, and reproduces it as given. Their own policy regarding odd lots is not a bug, and is documented in one of their memos if you search for it. They simply (understandably) want to get rid of odd-lot trading on ARCA. I'll note, too, that ARCA watches out for what they perceive to be abusive odd-lot practices, like people that hit for 1 share a bunch of times to paint the tape, or hit you for 1 share to annoy you or make your order disappear, and they send exception reports to your firm to warn about the practice.
IB does allow ARCA odd-lot orders, provided they close an existing odd-lot position. IB does not allow any other ARCA odd-lot order. I still don't see what ARCA gains by treating odd-lots different from mixed-lots. It doesn't make any sense. I still think it is a bug. If ARCA wanted to eliminate all odd-lot trading, then what is stopping them from doing so?