I'm not particularly concerned about a GP not telling me something about my child. I'm more concerned about the GP sharing (non safeguarding concerns) information with the named person that the child (general) doesn't want shared with their named person.
The court did seem concerned that there is not specific instruction in the legislation as to what should trigger an assessment. There is reference to assessments having been carried out on receipt of information, but nothing specific as to what the triggers are, leading to (what sounded like) concern that ad hoc assessments could be carried out without any basis for them.
I did find it entertaining when the QC proactively raised the point that it should be noted that the legislation did pass with an overwhelming (or similar words) majority, only to have the court ask several times what that had to do with the legality of it. Eventually everyone agreed that it had nothing to do with the legality. 
(As a side note, I read the notes from the Scottish court case and the judge there did think it worthy of mention, so perhaps the two courts are taking different views on some points...)