I've never experienced issues with the auto-grow setting of the text area and I took a quick look in the latest version and everything seemed to be working as intended. Maybe you're experiencing a caching issue? Try clearing your browser cache. Alternately, try to pin-point what might make your text area work strangely. It is nested in a strange way? Is it hemmed in by other widgets? If so, try stripping away elements until the auto-grow feature starts working. At the very least that might tell you which combination is causing the problem.
Could there be some custom css that is crippling the functionality?
Regards,
Ronald