Yeah, there's clinical backing for at least some of it.
The 20 seconds, 20 feet part is closely matched to eye exercises for people with certain types of nearsightedness or eyestrain. One example for nearsightedness is "close, middle, far" practice, where you cycle your focus across three visually-adjacent objects at different depths, which forces quick refocusing without saccades.
This has been pretty consistently shown to help strengthen muscles and improve refocusing speed. I haven't seen CVS-specific results, but for now I'll trust that treatment for older syndromes is a good start.
The 20 seconds, 20 feet part is closely matched to eye exercises for people with certain types of nearsightedness or eyestrain. One example for nearsightedness is "close, middle, far" practice, where you cycle your focus across three visually-adjacent objects at different depths, which forces quick refocusing without saccades.
This has been pretty consistently shown to help strengthen muscles and improve refocusing speed. I haven't seen CVS-specific results, but for now I'll trust that treatment for older syndromes is a good start.