The Different Ways of Holding A Pencil

Samuel has not been very good in his fine motor skills. He doesn't know how to hold a pencil until he turned 3. He was only able to write in a proper manner when he was at the age of 3.5.

He was abit slow and his writting was very light (you can hardly see), as he doesnt have the strength in his fingers with his right hand. All the while his school teacher has been teaching him with his right hand. Only at a very later stage the teacher notices that he has more strength in his left hand.

Since no one notices that he could probably be left handed and after sometime of right hand training, he is now a right handed. But sometimes without him realising it he will write with his left hand. Only when he starts to realise it, he will changed it back to use his right hand.

A few days ago, his mandarin teacher pointed out to me that he is not holding a pencil in the correct way. We did not notice or realise that he is not holding a pencil correctly.

Can you see the way he holds pencil? His "tallman" is on top of the pencil instead of at the bottom of the pencil.
I tried to change his way of holding a pencil but he complaint that his "tallman" is in pain if he puts it at the bottom of the pencil. Is this an excuse or is it a valid reason ?
Jesse surprises us by holding the pencil the right way since 1. She was able to hold the pencil and scribble hard in her doodle board. We thought that she learned it from Samuel. Only now I realised she must have picked it up from somewhere else.