Help with box volume/fill for junction box provided with LED recessed light
Bonus question: 334.5B is not a statutory waiver, it's to let you off the hook if the task is not easy, or if trying would risk mistakes (like trying to reach through a 6" hole with a staple gun).  If it's easy, you gotta do it. 

On your splices, the fill rules require: 


1 "wire" covers all grounds
1 "wire" covers all cable clamps
1 "wire" per actual wire brought in


So I count 6 wires.  14 AWG calls for 2.0 cubic inches per wire or 12ci.  Since this is part of equipment, I would expect the provided wires would be included in the cubic inches the manufacturer states.  

However I note a  &lt; $ 10/light price point. I also note their website is very marketing oriented, and has absolutely no technical sections, in the ordinary way a site like Eaton's or Lutron's would.  On the other hand, the site is perfectly competent, with none of the teeth-clenching English mistakes typically seen in overseas "makers", so I don't know what to think.