The security problems for io_uring or for any other system calls exist only when an adversary has access to those system calls.
Whenever you write an application for internal use, where there is no possibility for an adversary to interfere and control in any way the arguments of the system calls, there is no reason to avoid io_uring or other risky system calls.
Defense in depth through sanboxing is there to make sure that even an attacker that get some amount of undue privilege will not be able to do harm. At this point we've learned that all existing systems will have vulnerabilities of some sort, so defense in depth is the only credible security posture.
Whenever you write an application for internal use, where there is no possibility for an adversary to interfere and control in any way the arguments of the system calls, there is no reason to avoid io_uring or other risky system calls.