I think I read that discussion, the odds are a tenth as high for smashing compared to the odds from damage by fire, and the odds are lower still for diesel tanks, and much higher for hydrogen gens.
But yeah, apparently the odds were nerfed but still high enough that a mob of undead attracted to a running engine stand decent odds of getting a lucky hit to the gas tank before it takes enough impacts to smash it into being a leaky piece of scrap. Likely also depends on how strong the offending zombies, though unless bash damage affects the odds it’ll be an inverse sort of thing, as less bashing damage will mean more hits and thus more rolls to determine if it’ll go off.