This isn't a bug, it's the way the TCC parser works. It could be changed, but there would be a significant amount of parser rewriting involved (and an as-yet-unknown number of new compatibility issues that would arise).
Redirection occurs before back quotes are processed and removed. (Back quotes are removed after the command name and type (internal or external) is parsed and just before control is passed to the command.) So TCC is looking for the output file name for the redirection, and scans everything up to the first invalid filename character (which in this case is immediate, as the first character is the backquote). So you wind up with an empty filename, and TCC complains.
I'll look and see if it's possible to add a simple hack to check to see if a redirected filename begins with a ` and strip it then.