My interpretation is far from official.

My opinion is that you are not adding or subtracting sail material. You are not changing the shape of the sail material. Any of these things would be a change that would be a problem

The other reason is because you can order a jib from the factory that has roller furler (vertical) battens. So you are just making your sail usable. To me this constitutes a repair type situation. You could send it to Elliot/Pattersion and they would put the same battens in.

You can order a new jib that has these types of battens.

No different to me than if you change your downhaul to make it more user freindly.

You are changing a sail to make it easier to work with. Not to gain a speed advantage. This is the key to me which makes it class legal.

They put the "loophole restriction" in to cover in case they didn't think of something to cover in the rules.

My opinion.