Are Rolex parts not provided by ADS/RS- Inserts, Bezels etc. aftermarket / Fake?

[Speed]

So I stopped in Shreve in San Francisco today - just for the heck of it.

Got in to a discussion with salesman about GMT IIs...Then on to GMT II Cokes / Pepsis. He tells me how popular Pepsis are right now. Says they are scarce / discontinued (duh). I say, you could always buy a bezel insert and swap. He looks at me like I am from Mars and says you can't get them...and when you go to sell the watch, the papers say what the original model was. I say I heard the old GMT papers did not. He goes on to say he's been selling Rolex for 20 years... any swears bezel insert you see online or elsewhere are fake. Only an Rolex AD / RSC can order the part.

What gives??? Are all the fine indy sellers here getting "fake" / aftermarket inserts etc. etc? I don't want to generalize, but this arrogant guy ticked me off.

As an aside, I said I was interested in the SS GMT IIC. Oh they just got one in. I was wearing my Sub when I was in the store - he did not even offer to show me the watch / offer to let me try it on. Jerk...But I digress.

Thoughts on the question I posed are appreciated.