The CC Word guide suggests this reason too...It's to suck up and filter mako.
And as shown in the FFVII Remake, apparently that's part of what's used to keep Jenova healthy and happy; a steady supply of mako energy.
Jenova Doll
A metallic likeness of Jenova that was placed in front of her at the Nibel Mako Reactor, which Sephiroth destroys during the game. The details of how it functioned are unknown, but it is assumed that it helped to process and filter the sucked-up Lifestream.
Nomura thinks it looks cool.
It's to suck up and filter mako.
And as shown in the FFVII Remake, apparently that's part of what's used to keep Jenova healthy and happy; a steady supply of mako energy.
In-universe, it's serving some sort of function within the reactor for passing energy to Jenova ...
But why did Jenova need Mako?it's serving some sort of function within the reactor for passing energy to Jenova