I think this is something that should be fixed.
If you make either fill loop action with write automation and fader movement - or just use the Alt click in range with select tool - you don’t get a node entered at end of loop.
If you have fill loop - I think behavior should be setting nodes at either end of loop -always. That is assumed selecting Fill Loop.
If automation nodes exist after loop range, it does set node at end of range, but not otherwise.
It assumes the behavior that I would fill till end of track - but operation was Fill Loop.
So you manually must enter a node after selection first before doing this operation.