Peva,
"But for me, it explained in particular why lawnmowers and other smaller engine devices don't tolerate aged ethanol fuel, whereas old ethanol fuel doesn't seem to bother running/starting quality of car"
Free water in fuel is rare, if sourced from a reputable supplier with a high turnover, keeping the fuel fresh. No engine, new or old, likes water in the fuel.
Older engines (fuel systems) even in cars, may not tolerate E in fuel - this is because the system may have components that the E will damage. O rings, hoses, floats, valves, etc are often damaged by E.
Any petrol powered engine (rated to use E blend) will run just fine on ethanol blend. High usage (regular refresh) is the best. Low usage, especially when tank below 75% full, for extended periods, is more likly to result in condensation (water) contaminating the fuel.
"....systems of automobiles are required to be sealed...."
ALL fuel tanks "breathe" atmospheric air - to my understanding no conventional fuel tanks are sealed. True they may have a higher degree of "sealing" than say a mower. If truly sealed. they would collapse as the fuel was used and or atmospheric pressure/temperature changes impacted on them. All air contains more/less water vapour that will condense on relativly cool surfaces. Metal fuel tanks are more prone to condensation than plastic.