Hum... You are aware that those are one where the attacker gains execution capabilities inside the sandbox and one hardware vulnerability that affects every single language, right?
Gaining execution capabilities inside the sandbox is already good enough to compromise its behaviour, e.g. everyone gets true back when is_admin() gets called.
Yes, but it's a complete mischaracterization to claim it's a failure of the sandbox.
On this specific case, it is quite a big deal to add write and execute controls to the WASM memory, so it requires further justification than "I can do stack underflow attacks on my C code". Even though "I can do stack underflow attacks on my C code" is relevant information.