I think BA.com puts in a 2 hour connection as a default, unless it has been fed a specific connection time for a particular location. Not all such combinations are in the system, and I'd imagine it would be tricky to keep all of them up to date.

If ITA Matrix comes up with the fare, and the connection genuinely is over MCT, then you can call up BA and they should be able to book it.

I have to say 90 minutes would be tight for me at ORD. It's doable if HBO and Global Entry but not an easy connection. I suspect QoC will give her version shortly!