That check sheet you posted, which includes multiple Triumph models on it, is not specific to the Rocket. The 2014 owners manual and the Triumph Rocket specific workshop manual both state a valve check at 10,000 miles. Nothing changed. It is 10K.
I see this kind of stuff on many sites because I have owned many, many bikes. I get why people don't want to do the checks. It is a pain and\or expensive. Some bikes need no adjustments for many thousands of miles. Some need them right away. I like to check mine to get a base line of where they are at. For me, it isn't worth a burned valve not to check it. A few hours and I know where the valves stand on clearance. Everyone has their own comfort level with this stuff.