Logic dictates that security-related patches will always be backported to LTS kernels; that’s what the LTS designation stands for ─ “long-term support”.
However, non-LTS kernels that are still in use will not get the patch.
Unfortunately neither the kernels nor systemd are taken from arch but built by manjaro team themselves.
Those advisories you linked to don’t carry any relevance for manjaro unless those issues were fixed upstream and new manjaro packages built incorporating these fixes.
Yes, all Linux Kernels (5.4, 5.10 or newer) with LTS got the path in the stable branch. But systemd 248.5 not. systemd 249.1 or new was fixed in the testing branch.