Groening actually did claim as much, and the quotes are accurate; he was interviewed on NPR/WHYY's "Fresh Air" with Terry Gross (who recently took a hit from NPR's own ombudsman for her abnormally hostile interview with Bill O'Reilly a few weeks ago, wherein O'Reilly endured 45 minutes before walking out of the studio).
Matt Groening on NPR.
Date: 2003-10-30 01:41 pm (UTC)http://freshair.npr.org/day_fa.jhtml?display=day&todayDate=10/23/2003
It's 13 minutes long, and available in RA or WM audio streams.