Hardcoded $append=FALSE in AuthcacheP13nDefaultCoreService::drupalAddHttpHeader()

I am implementing an additional response filter to add an extra Vary rule and noticed that I can not append the new header to the already set Vary: X-Authcache-Key. The reason is that $append is hardcoded in the internal call:

class AuthcacheP13nDefaultCoreService implements AuthcacheP13nCoreServiceInterface {
  public function drupalAddHttpHeader($name, $value, $append = FALSE) {
    // Right here...
    drupal_add_http_header($name, $value, $append = FALSE);
  }
  
  // ...
}

I expected AuthcacheP13nDefaultCoreService to just be a OOP wrapper for core functions, but it's already making an assumption here. IMO, it's best is to just pass whatever it got from the caller for $append.