Our 4 year old writes half his letters backwards. UKG starts in June

He has started writing on his own over the holidays, mostly his name and labels on his drawings. The b and d are reversed more often than not, and the S faces whichever way it likes. When I point it out, he rubs it out and writes it exactly the same way again. His sister probably did this too, but that was eleven years ago and I don't remember when it stopped. Is it worth working on this summer, or is it something UKG will sort out by itself?