Various gunmakers generally go for one direction and others go for the other and a few chop and change.
An engraver I use who does a lot of restoration work in between new guns says that MOST Northern gunmakers go for one and MOST Southern go for the other but I jiggered if I can remember which way round it is.....hang on....lets take a look...
In my gun store the following: (from the breech = left hander, to the breech = right hander)
Purdey hammergun: left
James Lang SLE: left
Joseph Lang SLE: left
Joseph Lang BLE: right
Greener BLE: left
Alex Henry HGun: right
Boss HGun: left
AJ Parker BLE: right
C&H BLE: left
Linsley BLE: right
Blanch SLE: left
Blanch SLE: right
Blanch HGun: left
etc etc etc
Draw from that what conclusion you may!
The only reason I can think of is that 'from the breech' reads better for a lefty and easier for his friend as a right paw and visa versa.