The lip of the inner race would normally go against the crankshaft and the washer is fitted from the outside after the crank has been inserted into the bearing, however, to do so on an engine that had a timing-side ball bearing apparently requires the opening in the crankcase to be enlarged. There's a factory(?) drawing somewhere that shows this but I can't find it at the moment.
I slip the ring in before I fit the bearing into the case. The spool goes on the shaft. When you introduce the crank into the bearing it may take some fiddling to avoid trapping the ring but not much.
I can't see how fitting the bearing the other way would work, fitting the spool to the shaft from the outside and entering it into the ring would be difficult. Fitting the bearing assembly to the shaft and then the crank and bearing into the cases might work, but why would you.
I've never seen cases with a bigger aperture to fit the ring from the outside, but it's a good idea.
PS. I'm trying to recall if my Harris Bonnie was fitted with a roller bearing, but I don't think it was. It's the only Harris engine I've opened completely. I do remember that I fitted it with a roller bearing afterwards. Can't remember if the aperture was bigger, it was a long time ago...
PPS. Why don't the Norton guys use these bearings but insists on letting the crankshaft sail between single lip roller bearings?