Its confirmed in the "fleet of worlds" series, which is cowritten, and centered around puppeteer's homeworlds. He actually writes puppeteer viewpoints in these books, and we get to see the "companions".
Niven is fond of retconning his own cannon, but I can't see him going back on this one.
Thanks. I haven't read a lot of Niven's later stuff, he seems (to me) to have lost something along the way.