I agree with that absolutely....if you overheat the engine for whatever reason, it will have enormous consequences.
No manufacturer can guard against that kind of issue.
So, if you had a SS waterlock that wouldn't melt from high temperatures, there would be no sign of trouble and then your engine would be f....ed.
So, you add temp monitors to alarm if the temp gets too high....
Why not just do things properly?...like CHECK the seacock is open before you start the engine, maintain everything properly, check all the hose connections regularly, be sure all the water pathways are clean on a regular basis.
Sure, things can go wrong no matter how meticulous you are, BUT at least if you ARE meticulous any issue should be minor and solvable before it turns into a catastrophe.
We have no problems with our Vetus waterlock...18 years on....