You mention it in your footnote, but objects don't necessarily live on the heap - they can also live on the stack, or in registers, or in vector pipelines, or not at all.

Also an interesting aside is that objects are never 'allocated on the stack'. As in you won't find the same layout of memory on the stack as you do on the heap. Instead objects are turned into data edges in the compiler's graph. It's much more abstract than literally doing an alloca.