Other reasons for 19 men could be it's who is available, some of our lads are not because of injuries and operations.
Or it might be RM's approach to friendlies.
Instead of using them in the usual way, with all the squad and a zillion interchanges which proves little, he will have all the squad
feature across the 3 of them.
This will provide in more match day environment and give a better idea of how the players are performing.
I think it's RM not being bound by tradition and showing his Rugby brain in action again.