You can certainly have additional camera assistants on a large film, including a Loader, 1st and 2nd ACs for other cameras etc. I guess it just seems to be implying that you could have a Camera Assistant on your shoot or a Focus Puller and Clapper Loader, which is not really the case, as they both are Camera Assistants themselves, and in general perform the tasks described as the job of the 'camera assistant' in addition to pulling focus and clapping and/or loading.
You'll never find a set where a Focus Puller only pulls focus or the Clapper/Loader only claps and loads. They both have enormous amounts of pressure and responsibility, moreso than most others on set.
I do appreciate the making of a video, however, many of my non-film friends don't even realise it's someone job to constantly pull the focus of the camera!