Generally, when a beginner cannot complete a single pull-up, the advice advanced lifters dispense is to ‘do what you can’ (i.e. do negatives, hangs, partials, etc.). I’m not saying this advice doesn’t work, but…
Why are the principles of progression different for pull-ups than they are for any other exercise? If this is truly the best way to progress towards doing full sets of pull-ups, why do beginners not use a similar progression for lifts such as the bench press? They could pick an arbitrary heavy weight that they cannot complete for one rep and use similar progression techniques (negatives, static holds, partials). Obviously, this is not the best way to progress in the bench press. But my question is why not, if the pull-up progresses using these techniques?
There are two possible explanations I can see:
Closed chain vs Open chain: Closed chain exercises generally use at least bodyweight, so they have a minimum load. But there are open chain versions of closed chain exercises that can substitute while the beginner is building strength (e.g. lat pulldown -> pull-up, bench press -> push-up, barbell row -> inverted row, leg press -> squat).
The total load of the movement is low enough that these progression techniques are more effective than traditional full ROM reps. But if this is the case, would the same not be true for lifters who have exceedingly weak movements in other areas (e.g. a lifter who benches less than the bar would do negatives, static holds, and partials)? For almost any other movement, the solution for exceedingly weak individuals is machines with very low load capabilities and not these more advanced techniques.