Redmine

We already know that the new subtasks feature only applies to issues in the same project. Even issues in subprojects of the current project are excluded, which seems to make little sense.
However today I discovered a corollary - if you take a subtask and 'Move' it to a subproject it has its parent field silently cleared. I understand that I have to choose between having it in the subtasks list OR having it in a different project, but I do not agree that this information should be silently cleared as many users will be unaware of this restriction.