Besides spec bugs, the seL4 treat model is focused on making sure components are kept isolated. They do not deal with most of what we understand as attacks on a workstation at all.

In fact, in a seL4 system, most of the vulnerabilities we find on Linux wouldn't even be on the kernel, and their verification logic can't test something that isn't there.

That said, the seL4 model does probably lead to much better security than the Linux one. It's just not as good as the OP's one-liner implies.