Well, the journey planner will tell them that, but this is nothing new, there are plenty of situations where the journey planner will indicate a non-connection when the connection is, in reality, perfectly possible. For instance, the xx.27 Liverpool Lime Street to Manchester Oxford Road stoppers don't officially connect at Oxford Road with the EMT Nottingham/Norwich trains, but in reality they do, since
1) the two trains pull into adjacent platforms at Oxford Road;
2) the EMT is trapped behind the stopper.
People will quickly tumble to the fact that BPS-CNE, CNE-OMS and OMS-BPS are effectively going to be through services. Incidentally, because Preston is (I believe) an 8-minute interchange station, what you have said about OMS-BPS applies also to BPS-CNE and CNE-OMS. I have checked the journey planner and found that all those links ostensibly include an hour drop-back at Preston.
I really can't think why the above aren't (apparently) going to be advertised as through services, there have always been plenty of instances of a through journey being possible in one direction but not the other.