On the one hand, you are right, and I rather meant "not exploitable", since technically the vulnerability is still there. On the other hand, yes, any security does rely on you not doing something stupid like "curl | sudo bash".
> "In-VM attack only". That's disingenuous.
It's really not. Hardening of guest OSes is out of scope of Qubes. You are supposed to not combine trusted and untrusted actions in a single VM, so intra-VM security is really secondary. I really recommend you to read my link about organizing the workflows.
You have a good point concerning the integrity issues though.