https://upsidefoods.com/blog/animal-component-free-upsides-cell-feed-breakthrough-levels-up-the-future-of-cultivated-meat
This is apparently from one of the companys that Works on cultivated meat.

According to them, they got the animal cell free nutrition working. And use it for their production.

Since its from the company directly, You should take it with just as much of a grain of salt as the other article.

But, they have a very convincing argument:

The bovine cells are the most expensive part of the production, and using them for production purposes would be prohibitly expensive.

As cynical as that take is, to me thats the best argument that animal cell free meat will be the rule instead of an exception for cultured meat.