The new crewing levels are well within the limts for minumum crew for safetly isuues.
1x 50 pax on narrow bodied aircraft.
Any well managed crew with good team work can operate with 3 crew on a 319 on any route when there is only a bar service, all BA domestic services are single class.
The LCC's operate with minumum crew but they offer food as well as drinks that the pax has to pay for which is very time consuming collecting money from every pax served.
That is something BA crew do not have to do, no food (other than a biscuit or packet of nuts) and no collection of money for the drinks. Working the tourist cabin on a BA short haul aircraft on flights of 2+ hours must now be easier than ever before.