it isn't brainless :

"a baby version of yourself with only enough of a brain structure to be alive"

"A key inspiration for Schloendorn is a birth defect in which children are born missing most of their cortical hemispheres; he’s shown people medical scans of these kids’ nearly empty skulls as evidence that a body can live without much of a brain. "

That looks like hardware firmware vs. software. The clone would come with the firmware. Giving that the brain ages too, one can later want for the lower level brain parts to be refreshed too - i.e. amigdala, lower level visual cortex, etc - to come with the clone on top of the firmware.

For getting spare parts one would have expected that growing individual organs would come first, yet it may happen that growing them all together as such "brainless" body may be simpler.

Ethics-wise i think we're going into pretty nightmarish scenarios - as mentioned in the article women will be used as surrogates, and thus a multi-billionaire today can already clone himself, CRISP-in brain suppression (we'd like to hope that they would do it), and get such a body-clone as a source of parts.