I asked about this on Twitter.
Response:
this is flight is usually operated with our Euro Traveller and Club Europe cabin. It may be an error with the app or possibly a large aircraft is being used. Unfortunately we wouldn't be able to confirm in advance. Let us know what happens!
I'll put it down to an IT failure and will make sure I grab some lunch to eat en-route (my experience of BA BOB is of very little being available).