Anamorphic lenses : PRIMARY FOCUS MATCHING
When using an anamorphic adapter with a taking lens, the two lenses must be focused separately in order to sharply render the subject. In broad terms, if the subject is 3m away from you, then the taking lens must be focused at the three metre mark, as well as the adapter. In real terms each lens affects the others optics slightly so the focus scales might not entirely coincide. This doesn't matter too much as you will be focusing visually through the viewfinder of monitor.
With my single focus setup, this coinciding the focus of both lenses must still take place. Once it is established for one distance, however, it should stay consistent throughout the focus range. But in order to get that set in the first place, there must be provision to adjust the distance between the front element of the anamorphic and that of the taking lens. Once sharp focus is achieved for a particular distance this adjustment is locked down and only needs to be repeated if something gets bumped out of position, for example.