"must remain immobile in relation to the sprung part of the car"
What does that mean to you?
To me, it means one part of the bodywork can't move in relation to another, whether by flexing, or whatever else
This more or less means the same as “must be rigidly secured” or doesn’t have any degree of freedom. Important is that the rule speaks about a part. It does not say every single point of a part must remain immobile. That’s how the rule should be written to be applied for flexibility but it is not. Possible the rule makers didn’t even thought about flexible parts when they made that rule and it is not even necessary because there is a own chapter in the rules covering just flexibility. By the way it wouldn’t make sense to spread this rule over several chapters of the rulebook.
But how should we handle the wording of this chapter “every part must remain immobile”?
The complete front wing including the end of the nose can be seen as single part. This complete part must be immobile to the rest of the car. This can only mean there is no movement allowed in the contact area between nose and tube. If the part changes its shape is not relevant in this context because changing of shape or flexibility is not forbidden per se. Otherwise there would be some conflict in the rulebook between 1.15 and 1.17 which is not the case because 1.15 speaks about attachment of parts and 1.17 of flexibility. Things might look different when you attach another part to the end of the frontwing. This part would in fact have some movement because the wing bends down. That would be the mass damper case. The spring is allowed but not the mass on its ends.
As you see you can easily get some conflicts with the wordings of the rule 1.15. I think this part of the rules is written very bad. So there really might be some clarification and change of this rules needed to make clear its just talking about the attachment and clarify what they understand of immobile and how they want to test it. Until now it seems some common sense has to be applied here. A screw attachment can be seen as rigid attachment even when the screw might have some minimal elongation. It’s the same as a rock can be declared incompressible/without flex even when it has some minimal compression under very high pressure. We are definitely not talking on atomic level here.
Like it is written at the moment the rule 1.15 can not be applied to flexible parts. There is the phrase: Nulla poena sine lege. No punishment without a law. It is not RedBulls fault that the rule is written badly. Isn’t it quite bad that engineers have to teach lawyers how to write proper rules?