There was a movie I saw many years professor Richard Campbell traveling from Bali to Miami to graft these. As soon as he landed in Miami he went straight to grafting within few hours. All grafts were unsuccessful. And not compatible with Indica. He knew it. So, he had Wani seedlings from somewhere first.
I buy them every week, but not very big fan of it. It's just nice to taste something different and unique time after time. They are very variable. So, grafting is recommended for good quality.
Actually this thread prompted me to research where grafted trees are available in Bali. I think I found the source but details of location are a bit murky. I think I'll go and look for a place.
"One of the most specific cultivars and has great potential to be developed is Wani Ngumpen or often called Wani without seeds. It is called seedless wani because 90% of the total fruit does not have seeds. The marketing prospects for Wani Ngumpen fruit are very promising because the fruit is seedless, the flesh is thick, the taste is very good with a distinctive taste, and the price is 3 times more expensive than the price of other cultivars"