The bearings may physically fit 2ways, but they can only fit together 1 way. The outer larger part is called a race.The inner smaller part with the rollers is called the cone bearing or cone for short. I have never seen the cone pressed onto the spindle. They have always come off with my fingers. The race is always a light press fit. If you replace it, you will have to check the rotor run out. If it is out of spec, the rotor will need to be lathe-turned.
But here's the deal: if the race is still tight in the rotor, and shows no physical damage and has no visible bluing on it, Then I see no reason to change it.If it is damaged or blued, well then new is the thing to do.I would only replace the rotor if the center-hole will no longer accept the press fit. Sealing the seal is not a big deal.
I have noticed that somewhere along the line, replacement rotors are arriving with new races pre-installed, making it easy for you to bolt them on. That's a bonus.
