Most toners work faster and deeper when they are more concentrated. Polysulfide toner is an exception. As weird as it may seem, this is documented in books that most consider authoritative, including one from Tim Rudman. I saw this with my own eyes, too.
Say you have a polysulfide (one step brown) toner diluted per specification. You put your print in it to tone. It starts to tone. Say stop at a half way point then put the paper in water or HCA which is basically a weak solution of sodium sulfite. The rate of toning speed picks up. In my own experience, I had a print that toned for 4.5 minutes. In wash water, it actually toned to completion in just a minute or two. If I wanted to do the same level of toning in polysurfide step, it took more than 32 minutes. (my toning test ended at 32 minutes) So this is more than the usual toning with remaining toner in paper situation. The rate itself goes faster.
I wanted to stop the process on a dime, so I had to make a much stronger solution of sodium sulfite, 10%. In this solution, I observed the toning to stop on contact. In fact, to my eyes, it looked like it undid about 30 second to a minute worth of toning already done. I tried this which HCA because it's basically a weaker solution of sodium sulfite. It didn't work. The process sped up like I explained in previous paragraph. I was told by few here that at less than 5% concentration, stopping effect won't take place.
Roger and I had a discussion about this a while back. It's true there has to be a point where this weaker-the-faster holds true. Otherwise, a drop of toner in an ocean can tone everything in sight. He uses his toner much weaker to begin with and doesn't observe this phenomenon. I use mine at the dilution on the bottle. I see it every time.