It is an interesting question and worth discussing it within TC members. In terms of this particular function, it is so specifically developed for line tracing, and thus I will say no, you shouldn't use it (also even if you do, this will definitely not be close to enough for solving Rescue Line. And I think it is actually easier to make your own once you realize the inner workings of it. A very big benefit of it being you know what is going on rather than a black box).
So that's the straight forward answer. But there are loads of PID integrated commands in various software environments and we cannot keep track of everything.
There is no doubt that high level software is super useful, and is hard to draw the line for ok/not ok because at some point everything is a black box (e.g.: the lego Mindstorm NXT is a massive black box that people use for granted) and if we try to understand everything 1) nothing will be done and 2) you can't even do that in the first place.
The reason why we do ban these things is not because we want to be enforcers but because RoboCup Junior is an educational based competition (as opposed to something like a research based one), and we want students to come up with creative solutions that they really know how it works. From personal experience, a lot of these tasks can be done with extremely simple mechanisms and algorithms. At the same time, we are excited to see teams use complex technology; but with an understanding to some extent. The aim is to educate clever and smart robotics engineers, that can understand the inner workings of a device to a certain deep level rather than a simple user with a black box.
Sorry for the long reply (slightly diverging from your question), but it is something important to put out there I think.