I think that's correct behavior. The browser interprets AAA as part of the path, not an arg, and puts my_control.html at the end of the path.
It's always a good idea to use URL() helper. ie:
<a href="{{=URL(c='default', f='my_control', args=['AAA'], vars={'id':
'9'})}}">
c= and f= are optional.
Also, my_control is better called a function.

