Your instructor is full of shit.
Really? Do you even know how a cat even works? According to your own words, you don't:
The PCM is continuously writing to the adaptive tables to maintain a given air-fuel-ratio under given conditions. It doesn't start or stop doing so at any particular mileage.
Disabling the EGR will have no effect on your cat converters. The tiny amount of exhaust gas that would have passed through the intake (and back out the exhaust port) just goes out the tailpipe along with the rest of the vehicles exhaust.
What kills cat converters is vehicles running rich for long periods of time. The cat converter will burn the un-burnt hydrocarbons sent to it by the motor causing it to run very hot (think: throwing gasoline on a camp fire). Eventually the sustained high temperatures will cause the substrate to melt and break down.
A clogged cat converter will strangle an engine. Volumetric efficiency drops off causing a loss of power and poor running. The more clogged the converter is, the worse the motor will run until it simply cannot pump any more gas through itself and stops running. A clogged cat cannot blow up an engine.
While I do agree with you that a cat will clog a car, causing it run poorly and then to quit, you, sir, fail to understand why.
Do you even have a basic concept of chemistry, to understand the process?
The catalytic converter does not "burn" what goes through it; there is no combustion or ignition within the catalytic converter itself. The reason why a catalytic converter feels warm is from the heat of the exhaust, first of all, which was produced in the engine itself; the second reason is that, during a catalytic conversion of CO and NOx to nitrogen, carbon dioxide, and water, there is a conversion that takes place that also includes a rise in temperature that the catalyst is, itself, unaffected by (catalyst: a chemical compound that acts as a reagent during a chemical reaction that is itself unaffected by that reaction).
While the high temp sustained in rich-running cars will cause the catalyst to eventually melt and break down, in a properly running system, this does not happen. Rather, the heat from the exhaust gases themselves, whether or not the system is operating correctly or not, is what causes the substrate to melt and clog the system.
As to your first statement, if that were the case, why did he show me pictures from the shop he worked at where a customer had to have an engine replaced, due to a piston blowing out of the motor because the cat had gotten clogged? In essence, the way he explained it to me is that the pressure blew out the piston with the highest compression through the oil pan, with all the other seals and gaskets still holding, just like you have the same results when you have a coolant system failure--wherever the system is weakest at, the pressure will blow at that point first.
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