They need clearance to allow for manufacturing tolerances where the centreline of the crank can be not quite concentric with the centreline of the pump gear, I made yours a little tighter Marko because I sat the pump on and checked where it was running before I made the collar. The clearance isn't a problem. The standard rb25/26 gears don't break and they run the same. SR20's, CA18's, Toyota 4AG's, Hondas and others run the same drive setup and rarely have problems. Nissan TB48 engines have a similar problem when they're pushed. I think it's just down to the material used. Powdered metal is used for a lot of parts that are hard to machine cheaply, almost all oil pump gears are made the same way. To mill an N1 outer gear you'd need to use a <2mm diameter cutter which just isn't workable for that type of job.
I don't know why Nissan made the N1 pump with a smaller diameter outer gear which makes everything a little thinner and easier to break. I just fitted a set of the JPC gears to an N1 housing and they are good, same side clearance as factory and about .001" more clearance between the gears. The engine is from a hillclimb/circuit car still running the hydraulic tappets so I didn't want to go for a bigger pump.