I'm just saying that you've heard wrong. "if the indult is in a diocese whose bishop permits altar girls at the NO parishes, and a girl requests to serve at the indult, she must be permitted to do so" - a priest is not obligated to allow any girl servers, even if the bishop permits them. The congregation is a different issue; obviously they cannot order around their pastors.
It's not obvious to protestants.
But it is possible that while the law might prohibit a priest from being forced to use altar girls, what I "heard" might not be "wrong" since we know that the law oftentimes does not reflect the reality.