I'm not really knowledgeable about malleable pipe couplings, however, I
had a Husqvarna off-road motorcycle that had malleable clutch and break
levers, shift pedal, etc. I never had to replace any of them, and I
bent some of them nearly double. They would bend back, never cracked or
weakened in any way. I rode and raced it for well over 5 years and
crashed it a lot. What a refreshing change from the Japanese bikes that
would break control levers just falling off the kick stand. My point is
malleable would be a good thing if there is any stress, and I've broken
a few non-malleable iron pipe fittings and I haven't done all that much
plumbing.