Board Thread:Naruto Discussions/@comment-32617252-20170827195402/@comment-30323490-20170830142320

You don't need rinnegan to absorb chakra. There are other methods. It was stated that Kinshiki can indeed absorb chakra, which is also sustained in the anime, when he return to Momoshiki with the pills, probably meaning that he already absorbed the chakra and turned it into the pills.