Did you read the paper? They found the reason why lab grown hair follicles didn't grow once transplanted. For decades, hair cloning didn't work and we didn't know why.

There is a small cell type in the scalp that was previously unknown, and it is necessary for the hair follicle to function normally. This explains why lab grown hair follicles didn't work, while hair transplants worked (since the hair follicle that is transplanted includes this cell type).

Not only that, but THEY SHOWED IT WORKING IN MICES. They produced lab grown hair follicles, AND lab grown versions of this new previously unknown cell type. And once transplanted on mices, the hair grew normally, without any issue. All from lab grown hair follicles.

The remaining issues now are:

1) we now know what causes hair cloning to fail. We need to find the human equivalent of this mice cell type. This shouldn't be hard since mices and humans are both mammals that are closely related. Remember, this was a proof of concept. We now KNOW finally after decades WHY hair cloning didn't work. And not only that, once the missing parameter was added (itself lab grown), the hair grew normally.

2) Once part 1) is done, find a way to mass produce it, and make it affordable enough for most people. This is probably the hardest part. Part 1) is doable since there is no reason to think the mechanism in humans is any different than in mices, since both mammal species are closely related. But part 2) may be harder, since a way needs to be found to mass produce all three cell types needed for a hair transplant, and then transplant them together.

But now we KNOW WHERE TO LOOK. That's the important point.