Especially since sudo is generally quite short lived. Unless it is leaking a significant amount of memory waiting for authentication that never comes it is insignificant. It would actually be pretty easy to argue that sudo just shouldn't free memory at all. This would be better for security (all pointers live forever) and possibly faster as upon exec the kernel can just wipe all state rather than having free carefully account for the releases.

no general purposd language can guarantee a lack of memory leaks

You're going to summon every Rust enthusiast on the platform