Hi! This is probably not going to be a very useful reply, but I do remember asking the same question when the toggle was first introduced, and I was told that it's expected for some apps to not have that toggle.
I believe that hardened_malloc is only available for 64-bit apps, so if that's true, it stands to reason that the 32-bit version wouldn't have any memory corruption bugs caught, and therefore would not be made to crash by hardened_malloc.
I will try to confirm the above information, but until I do, please take it with a grain of salt, as I'm not 100% sure this is how it works.