Intermediate and certificate checks in BIG-IP LTM

Ah, gotcha. That makes sense. But no, newer versions do not perform a check on the CA chain in the SSL profile.

But, as of 13.0 there's a new feature called "CA Bundle Manager" that will auto-build and maintain CA bundles, which in your case could update the bundle automatically to include the g4 CA cert.

Ref: https://support.f5.com/kb/en-us/products/big-ip_ltm/manuals/product/bigip-ssl-administration-13-1-0/3.html