An alias is an alias I think, wether is uses subdirectories or not should not matter.
DNN provides support for using multiple domains on a website, and you can set them up as cannonical, redirect or none.
When I set it up as a redirect, I expect it to redirect to the standard alias.
If that does not work, you should not say it is not supported, you should say thay it is a bug.

I assume, this is caused by missing subdirectory for the 2nd alias, but I haven't checked it out.
Personally, I would suggest preventing different subdirectories being used for same child site.

---

Cheers from Germany,
Sebastian Leupold

   

Speed up your DNN Websites with TurboDNN