A little bit of…
A little bit of clarification that might help.
A steel structure is very ductile. When overloaded it will be damaged by bending. The bending will typically be recoverable by bending it back. Steel car bodies are repaired/straightened all the time of course.
An alloy casting (however mega/giga/hyper the gobbledegook) is mostly not ductile, so when the load rating is exceeded sufficently, it'll snap fully off with loud boink. And when the two bits are offered up to each other, they'll fit neatly and show some small stretching during the tearing/fracture.
Cars have a hard life, mechanically - even more so when towing.
A steel structure will harden/fatigue through repeated abuse and displace/tear progressively in general. And can be welded back on.
A cast alloy structure will go all at once, and respond badly to cyclic overloading. And respond badly to welding, in general.
QED, don't make car chassis parts out of light metal alloy by casting.