And surely easy to refute, if they were public? Internet Archive would at least have scraped the channel's page.
TFA links to https://www.youtube.com/channel/UCGPZJTVIpNe-hroLo-CQ9wQ/vid... which currently 404s...
But which indeed did contain many videos... https://web.archive.org/web/20201101020416if_/https://www.yo...