Dear list friends,
I have studied and thoroughly documented photographically the caves in question. The earliest major caves e.g. Pitalkhora and Bhaja are such detailed copies of wooden models that even joints in the wooden prototypes are are carved into the stone. Further the walls in the vihara at Pitalkhora were carved way too thin for stone and collapsed. Details of wooden architecture, e.g. arched bracketing, continue until the end of the fifth century.
As an occasional wood worker (mostly furniture), I can see exactly how the wooden structures prototypes would have been built.
Unfortunately for the author, the rafters at Karle are actually wood (presumably teak)
The joining of slabs of wood to make the the curved beams is clearly visible (simply they were not bent wood rather butt dado joints). his entire premise is simply armchair speculation.
John