Linked Issue validator not triggering

In Behaviours, it appears that it isn't possible to trigger a script when an issue is linked/unlinked.

To replicate:

1. Set up a transition containing the 'Linked Issues' field.
2. Create a Behaviour
3. Add field 'Linked Issues' to the Behaviour
4. On 'Linked Issues', 'add serverside script', and enter 'log.error("Script ran");
5. Test the transition, setting 'Linked Issues' and entering an issue key in the "Issue" text field. Nothing happens (no message in logs).