Maybe this grape cultivar was really successful with this form of propagation and the producer fears an end-user (or nation state) might do just that, but they taste so good, they went to market anyway with something they may not be able to control.
As a biologist, I assure you not any tissue or plant can be casually tissue cultured. Maybe in theory, but in practice I wouldn't want to be asked to try and turn a bit of woody apple fruit stem or sepal tissue into a viable clone!*
Far easier to just go to the farm during the right season and grab yourself a scion to graft.
*I'm getting enough of a headache from one of my side projects trying to tissue culture some plant tissue that actually has a practical purpose- I'd rather stick to grafting when I can to avoid unnecessarily complicating my life!
https://www.bbc.co.uk/bitesize/guides/zx6g87h/revision/4
This technique seems hit or miss with apples.
https://www.tandfonline.com/doi/pdf/10.1080/12538078.2010.10...
Maybe this grape cultivar was really successful with this form of propagation and the producer fears an end-user (or nation state) might do just that, but they taste so good, they went to market anyway with something they may not be able to control.