I suspect it was simply a question of where to use these 737s until the transfer to Rouge (and subsequent refurbishment to Rouge interior).

No point in updating the interior to Mainline specs for such a short period of time. Operating as mainline flights will generate frustration (most especially here on FT where any decision the airline makes is automatically met with 'the airline doesn't care about its customers' or 'they don't know what they are doing').

So Express fits an all Y plane that feeds traffic to hubs. The exception being the KIN route, but having flown that route a few times (and know people who flew it regularly) they had a daily Rouge 767 that was full in Y and empty in J, so it fits the bill and not a prominent route tourists or business travel.

I don't see the objections especially as this is temporary.