If by "dogging it" you mean that he was clearly the best player on the Spurs SL team and was flat-out dominant at times doing everything from scoring to distributing to rebounding....then yes, he was "dogging it".
The "18 second" comment you read was probably another Ludden dish, who has about as much love for Butler as I do for the Opera.
I do agree that his lack of stamina, and lack of motivation/spirit during the regular season probably got him bounced from the team. That's what made him less of a "Spur". ...