I couldn't find any evidence of this at the Grand Canyon website. They
discuss the age of the canyon on the website in the FAQ section: http://www.nps.gov/grca/faqs.htm#old
Who knows which version to believe? Even the guy who wrote the 'Noah's
flood' book gave the official scientific version of the formation of the
Grand Canyon when he worked there, so I doubt that any of the park rangers
are spouting nonsense.