Head gaskets especially should last a minimum 100K because the engineering difficulties have been conquered long ago. GM gives a 100K waranty now because it knows darn well that only a few (standard mean deiviation and all that statistics stuff) may fail prematurely. A resevoir bottle (like I stated may be trivial) that does nothing but sit and collect any coolant overflow from the radiator should last pretty long- and they do in every car I have owned with an overflow bottle. Heck, why doesn't GM use old coke cans. On various threads, I read of everybody's screaming about cheap interiors and cheap plastic. I guess most people identify with what is in front of their noses but what lies underneath (the bearings, gears, radiator) is more of a tell-tale of the car's quality. But a good looking interior will sell cars and please the salesperson who may not care what happens after 3 years' service (or after the deal is sealed for that matter).
It's a Chevy and this is a Chevy dealership. So, if Chevy designs ground effects, the Chevy service should be able to deal with ground effects. In this case, I think it is more a mechanic's fault not locating the lift correctly. I don't expect the mechanic to lay on the ground--that is not an efficient way to work on cars.
As far as reading a warranty, there is a certain amount of leeway that is understood. For example, after 3 years the fenders fell off. Would you say that this is reasonable? How about the fuel tank straps failing? Let us go one step further--the car catches on fire due to faulty injectors? As far as you are concerned, all the GM cars could experience such problems with no repercussions. When purchasing a vehicle, even though the warranty says 36K/3yrs, the buyer sees this as nothing more than "okay, all those little things that are not caught on the floor will be fixed". Do you remember Dodge's transmisson problems? As I recall, Chrysler extended the warranty and was very generous about listening to the customer. The problem, if not handled with some sense of reason, could have shut Chrysler down. Oh, by the way, in the mid-80's, I had a visit to Teledyne foundry in IN. They were pouring a 16,000 lb casting that I had designed. In the scrap yard (material purchased from companies and re-used), there was a huge mound and 4-5 gondolas of crankshafts. Some were still castings and some were machined. I asked and the fellow said "Oh, those are from GM". Mfr's have their problems but to stand behind the product shows the true colors of a company.