The built-in MacX Window Manager doesn't support the window animation after
the window has been iconified. In other words, all iconified icons become
inactive until de-iconified.
However, other window managers, such as "twm," support this feature even if
the client has been iconified. The icon still does animation as it is in
the regular window. For example, the "kalaid" client under "twm"
demonstrates this capability.
We suggest that you run the client under your favorite window manager.