Assuming that Abbott isn't injured, the only reason I can think is that we're slightly fed up with having to constantly rely on Abbott. Bailey was possibly laying a marker down for the other bowlers, saying "look, it's a number 11. We shouldn't need to have to be turning back to Abbott. You earn your corn by finishing this off yourselves".
Either way it has backfired. Abbott has to open after Tea, even if it is just for two overs.
If it wasn't for the poor weather tomorrow, I think the issue of saving Abbott for the second innings would be out of the window now. Because I would absolutely be batting on now. Try and smash 150 tonight. Trott has helped Warks eat far too much into our lead. But given that the weather is poor tomorrow, we still have to enforce the FO.