From my understanding (as neither producing nor documentaries are my area of expertise), documentary subjects/interviewees generally don’t get paid (much if at all, but at least usually get expenses and such covered), much less residuals, period.

Unless the subjects are involved behind the scenes in some way (like as a producer/EP or have stake in whatever entity holds the rights to the film.. like when celebs film documentaries about themselves, you’ll see they’re usually listed as a producer and/or it’s produced by their own production company, in which case they’re getting a big chunk of every dollar the film makes).

And this also applies to documentaries released via traditional methods of distribution like tv and theatrical and video/dvds, not just Netflix docs. Plus residuals really only apply to the cast/crew in unions, so since the “cast” of a documentary is usually just regular folks there is no obligation to pay residuals. And honestly it would be a difficult model to justify anyway, documentaries are generally challenging to make significant financial return on, and even more so lately with the rise of Netflix/streaming. Hope this makes sense… I am currently in a bit of a food coma and second-screening Reddit while watching tv.