I don't know anyone who says that. Most of the top 3B have spent some time at other positions. Beltre is a rare case who hasn't. He likely will end up #1 in games played and innings among all 3B which is impressive. He's not the hitter Chipper is but he has a legit argument as being the best defensive 3B ever.
http://www.espn.com/mlb/story/_/id/18503141/casting-my-2018-hall-fame-ballot-today
Even our own TV guys have used that term on air when showing statistics about how Chipper had most RBI's and passed Schmidt.