My eldest is now 20 and we were in your position when he was in P3/P4. His writing is AWFUL and I mean really, really awful. School did what they could but they were very much taking the approach that practise would make it all better and we spent hours doing those Teodorescu writing packs making loops and drawings and it was torture for him (and me). He was assessed by Occupational Therapy at that stage for a potential dyspraxia diagnosis - this is also now known as Developmental Coordination Disorder, or DCD. The OT lady was very nice, accepted that he had difficulties but wasn't "bad enough" for a diagnosis.
Anyway. All through secondary school he was allowed to use a laptop for doing exams, and both school and the SQA were happy to allow this without a formal diagnosis. That all changed when he arrived at university and was told no diagnosis, no laptops or digital exams. So at that point we had to pay £££ to see more OT people privately for a proper diagnosis.
So my point is really that if you suspect your child may have dyspraxia, the pencil grip and writing practise might help, but it might not. Think around other things which dyspraxic children have issues with ring any bells with your child - things like learning to ride a bike, learning to swim, tie his shoelaces took my boy SO much longer than other children and I only realised that when my younger children reached the same stage and mastered the bike riding in a couple of hours whereas it took him weeks. He struggled (and still does, hugely) with organising, prioritising, fiddling with things.Rubbish at sport, throwing and catching, learning to drive has been very challenging for him. There is LOTS of support for him at Uni now that he has the official diagnosis though with a whole Wellbeing team at uni running support and study sessions with software and techniques to help.
Long story short - if you suspect something like dyspraxia - and you can see the list of symptoms here
https://www.nhs.uk/conditions/developmental-coordination-disorder-dyspraxia/symptoms/
then I would STRONGLY ADVISE pursuing that now through either the NHS or privately, with input from school now when he's still wee and cooperative. I can recommend private assessment in Glasgow if that's any good for you, unsure about Edinburgh.