Factually all true.... you could have all RCBOs instead of MCBs and two RCDs. ... This means you would have circuit breakers with their own individual RCD built in. .... This therefore means if there is an earth leakage fault, only the one 'RCBO' will trip, whereas before one RCD would trip taking out several circuits rather than just one. .... If you can afford it....
However, to put this all into context, when I think about the (tiny) number of times during the 40+ years I've been living with RCDs that I have experienced an RCD trip due to an earth leakage fault, and the (again, tiny) proportion of those (extremely few) trips which have resulted in appreciable problems or inconvenience, I have to wonder how much additional cost (for 'all RCBOs') can be justified to balance the consequences of not having 'all RCBOs'.
Kind Regards, John