In general you are right, such preventive maintenance makes financial sense. Since he already was at it, he could also replace the crank shaft (or how it is called?) seal ring at the back of the engine and another on the gearbox, which are much more "critical". It is the same work and these rings probably will start to leak soon.
Half a year ago I did the similar work on my 1993 VW Vento 1.8 (aka Jetta III on the other side of the pond). It was just another way round: I have noticed some traces of oil and took out the gear box to replace the seal's which apparently started to leak. Since I already was at it, I also changed the clutch, since the rivets were just about to stick out of the lining (at ~100k miles). Traffic conditions here in europe are much harder on clutches :)
As for the bearing in this particular type of clutch, if it does look OK and accessible without removing the gearbox, I would not blame mechanic for not replacing it "just in case". It makes much more sense when bearing is near the clutch and is not accessible without separating the gearbox from the engine. Of course, good and honest mechanic would offer it and explain why.
Mine was also bluish, but hey, that's the nature of the thing. Friction allways creates heat, and heat changes the color of the metal :) On the other hand, mine was absolutely smooth, without any scratches. As long as the pressure plate is not warped and not scratched, I would tend to think, that these spots are just some dirt, witch landed on the surface after disassembly. Thats why it would be interesting to look at it after it is cleaned. In any case, the clutch disk does not look as it had such a bad working conditions.
Btw, it could also be, that soon-to-be-broken clutch finger did not disengage the clutch properly, so it was allways grinding a little bit. OP did mentioned, that clutch pedal was getting "stiff". Such spots could also be caused by some oily dirt, althrough I can't see where it could come from, clutch disk does look reasonable clean.
You think it would be a pleasant story to listen? :) The trust was damaged anyway, "totally worn" in my opinion does not much those pictures very well.