Your Voyager 1 graph [footnote 0, in the parent comment] shows two periods of particles-per-second drops to around 10 particles per second followed by a rebound and then a dramatic drop to 2 to 3 particles per second.
The Voyager 2 graph [footnote 2, in the parent comment] shows a single drop to around 17 to 18 particles per second and what looks like the beginning of a rebound. Wouldn't interstellar space be characterized by the drop to below 3 particles per second?
Is this the same issue we had with Voyager 1 where Voyager 2 is beginning the process of entering interstellar space but has not yet actually entered it? If not, why are the particle counts about an order-of-magnitude higher for Voyager 2 then they were for Voyager 1 in interstellar space?