There have been several recent comments on an older post at onemileatatime that address the question of a cabin change.
One states this was the prior language (my italics):
Changing Flight Award Tickets
Changes to origin/destination –
A $150 USD charge or additional miles will apply for a change to an eligible origin or destination on a MileSAAver or AAnytime award, (waived for AAdvantage Executive Platinum members using miles from their account). This additional charge or miles are waived when voluntarily upgrading to a higher award level in the same region.
That is confusing since the waiver is included in the change to origin section.
Another commenter was recently told there is a fee to upgrade cabin (which he was able to get waived).