This statement applies to heavy aircraft ie, the typical airliner. As we come down the size scale, certification reality reduces aircraft capability requirements. Indeed, otherwise we wouldn't have any small aircraft due to the prohibitive cost of ownership. For the low weight end of the spectrum, the requirements are a bit scant ..
Absolutely true, JT. I lost a good friend and three generations of his family in a Beech Baron incident many moons ago. Short story, he intended to fly the entire trip gear down due to an issue they had encountered in New England. He informed ATC, all OK. On climbout he had an engine failure which NTSB eventually attributed to a piston deformation in the manufacturing process which would not likely have been discovered in normal maintenance. Informed ATC he was heading back to airport, what could they say? With one engine, and gear down, plus making a turn -- crashed and burned in the woods some ways from the aerodrome. NTSB said while piston failure was root cause, "probable" cause was the pilot's error as he turned around with gear down and didn't aviate first to gain altitude before working things out. It'll be 15 years this years this summer and still gives me the creeps.