A post about owners who moved their hot water tank into the roof space without notifying the OC or seeking permission (the post has since been removed at the OP’s request) illustrated how this apparent annexing of common property roof spaces can happen, possibly quite innocently.
Did the apartment owners not know they needed permission or was it a case of it being easier to apologise after the event than seek permission beforehand? In any case, it was resolved with retrospective permissions.
Being asked to sign a document like the one described by the OP might have avoided this.