BIG-IP DNS Resource Record Types: Architecture, Design and Configuration

https://clouddocs.f5.com/cli/tmsh-reference/latest/modules/gtm/gtm_pool_cname.html

This is from the 17.0 docs which echoes what I said above without the additional context. It is always considered available b/c there are not health checks.

 static-target
 Specifies the member's name specifies a static DNAME rather than a name linked to a Wide IP defined on the
 system. This may be required if the target DNAME is not owned by the organization or configured on GTM. One side-
 effect of using a static target is that the member is always considered available for load balancing. The default
value is no.