We could make up some spectrum of proficiency and attach generic requirements of each but it isn't anything of a revelation.
Factors which measure sight reading proficiency could be asked of ChatGPT. Something like this shows how any real comprehensive measurement of an individuals skills would be quite personalised.
Note-reading ability
Finger coordination
Tempo and rhythm accuracy
Sight transposition
Musical interpretation
Memory and recall
Adaptability and flexibility
Sight-reading speed
Sight-reading accuracy
Chord recognition
Sight-reading dynamics
Articulation and phrasing
Sight-reading complex rhythms
Sight-reading different musical styles
Interval recognition
Sight-reading melodic lines and counterpoint
Sight-reading harmonies and chord progressions
Sight-reading polyphonic textures
Sight-reading ornaments and embellishments
Sight-reading pedal markings
Sight-reading special notation (e.g., trills, glissandos)
Sight-reading multiple staves simultaneously
Sight-reading advanced musical forms (e.g., fugues, sonatas)
Sight-reading at different levels of difficulty (beginner, intermediate, advanced)
Sight-reading with accuracy while playing at a different dynamic level
Sight-reading key changes
Sight-reading modulations
Sight-reading irregular or asymmetrical rhythms
Sight-reading extended techniques (e.g., prepared piano)
Sight-reading changes in articulation (legato, staccato, accents)
Sight-reading changes in tempo and meter
Sight-reading changing time signatures
Sight-reading complex chord voicings
Sight-reading harmonic progressions in different keys
Sight-reading accompaniment patterns while playing a melody
Sight-reading pedal transitions and changes
Sight-reading polyrhythms and cross-rhythms
Sight-reading repeated patterns and sequences
Sight-reading expressive markings (crescendo, diminuendo)
Sight-reading pedal points and ostinato figures
Sight-reading syncopated rhythms
Sight-reading left-hand independence and coordination
Sight-reading right-hand independence and coordination
Sight-reading complex time divisions (triplets, quintuplets)
Sight-reading complex melodic intervals
Sight-reading complex harmonic progressions
Sight-reading changes in tonal centers
Sight-reading chromatic passages and modulations
Sight-reading multiple voices within a single hand
Sight-reading mixed meters and changing subdivisions