I think you got the definition right, John, as I understand it. Don't think I've met many straight 'type collectors' in football myself but they're definitely out there somewhere.
I think type collecting is popular in baseball because of the massive amount of sets that were produced pre-WWII, making it extremely difficult to obtain even one from all of the sets even in a particular decade! We don't have that sort of issue with football cards so perhaps that's why you don't see as many football type collectors.
I know as a kid I was a type collector for cards produced earlier than the 70s as I couldn't afford to do anything else!
jeff