They are all composite materials, right? Can't they be manufactured in a couple pieces and fused together properly on-site, using technology that is a more economical as compared to designing and building new types of aircraft?
However, I understand that doing a composite/chemical joint basically involves setting up a mini-factory, since your joint quality will depend very much on being able to control the conditions. Mechanical joints require less on site infrastructure, but have an efficiency penalty (https://www.nrel.gov/docs/fy23osti/84397.pdf).
In any case, I imagine Radia is betting on getting enough volume to make the development cost irrelevant. In the end, you had to transport the roughly the same amount of material onsite anyways, in roughly the same form factor. The cost of a fleet of aircraft can be amortized over a huge geographic span wind farms, while also being attractive from the perspective of delivering replacements.
I definitely think segmented blades are a way forward, but I can also see Radia's argument. I can totally believe that the "real winner" is going to a combination of situation and execution.
It might be a bit of a chicken/egg situation, the materials science required to do without the full-size oven not being worthwhile without a transportable implementation of all the assembly and layup arrangement that would have to be done before, and the logistics not happening without a solution on the materials side.