He's right.
Giants 23, Cards 16, Yanks 15, Cubs 14, ....
http://www.baseball-almanac.com/hof/hofstat.shtml
Something tells me that 10 years from now the Yankees will probably be pretty close to the Giants in HoFers. However, the Yanks will still have way more WS titles then the Giants.
Don't know where Baseball Almanac got their info. Wikipedia lists 18 Yankee players who entered the HoF as Yankees:
Yogi Berra, Earl Combs, Joe DiMaggio, Bill Dickey, Whitey Ford, Lou Gehrig, Lefy Gomez, Joe Gordon, Goose Goosage, Waite Hoyte, Regggie Jackson, Tony Lazzeri, Mickey Mantle, Herb Pennock, Phil Rizzuto, Red Ruffing, Babe Ruth, and Jack Chesbro (as a N.Y. Highlander, the team that evolved into the Yankees). Still not as many as the Giants, but more than Almanac gives credit for.