Use "secret" to create a user specific variable wont't work

I have set up a project with QFieldCloud. In QFieldCloud, a secret was introduced. Scope: User + a project. The user Alice got assigned with the variable TESTVARIABLE - the value was set to “in chains”. In an editable layer of the project, the default value of field “myfield" is set to @TESTVARIABLE

In my understanding, when Alice creates features and pushes them, when the feature flows thorugh QFieldCloud, “myfield” should be set to “in chains” - but it stays NULL

Do i understand something wrong, or is it a bug?