Why do post functions work when backlog is shown on Kanban board, but not when shown in Backlog view

[Victor Grazi]

I have a post function in my Kanban board, that transitions all issues from backlog to todo, when an epic is moved.

This works nicely when the backlog status is mapped to the first column of the board.

However if I show the backlog in the backlog view, the post function no longer works.

Is this a feature or a bug? How can I transition linked Jiras, whenever the parent epic is moved out of Backlog, in the backlog view?

We are using Jira version 7.12.1

Here is a screenshot of the transition definition: