I in no way wanted to contradict your contribution or method, just add to it, also for the benefit of those who may not be as experienced. For those who want no image change, but wish to increase D-max, your technique is viable, to a point.
The only problem I have with it, is that it relies on a constant strength solution. In practical reality, a solution of selenium toner loses strength as the selenium is used up and times to reach the same degree of toning gradually increase. In your case, the time to reach D-max for the first 8x10 in a liter of solution and the 50th will be markedly different, since the effective strength of the toner will be less after a number of prints are run through it. This is not taken into account in your tests.
One could simply discard the toner after a certain number of prints had been treated per volume of toner and achieve a degree of repeatability. Unfortunately, this entails discarding a lot of still active, but weaker, toning solution, a practice I find both uneconomical and environmentally irresponsible.
Replenishing the solution is a much better and more environmentally-sound method than discarding toner with a lot of active selenium compounds. In your scenario, one could replenish at a certain rate depending on the area of paper run through a given amount of toner. This would work extremely well, but require testing to determine the rate of replenishment. Maybe you feel like doing these tests and posting another video :-)
For me, since I desire a change in image tone that ranges from simply neutralizing the greenish cast some papers have to adding a subtle but marked eggplant tone to the print, a visual approach is more useful. I tone with an identical untoned print in a tray of water next to the toning tray, and pull the print being toned when it looks right. Lighting type and intensity make a difference here, so I try to tone under lighting that I prefer for print display. Since I usually have multiple copies of a print that I am toning, I note the time for the pilot print and then tone the others to that time, keeping in mind that the toning times are slowly increasing. If I have a batch of, say, five prints, I am careful to keep comparing subsequent prints to the original pilot to make sure they are toned enough. It's all rather subjective, not the carefully controlled method you have developed.
This allows me, however, to replenish and save my toning solutions indefinitely, as I described in my previous post. I've just finished another toning session, and both my strong and weak solutions are doing just fine and the prints test perfect for residual hypo and silver. I've had these two jugs of toner for at least five years (possibly 10!) and have just added stock to the working solution as needed (when toning times become too long) and filtered them before use each time.
To answer your questions, I use primarily graded papers: Oriental Seagull, Adox Nuance, Slavich, Foma, etc. with some VC for times that the graded papers won't do the job (Kentmere, Adox). I see tone change as I tone on all the above papers. It's been a long time since I used Ilford products, but saw tone change on the papers from them I used also (Ilfobrom, Gallerie). In my experience, almost every paper will exhibit a marked change in image tone with selenium toner if the dilution is strong enough (although I have worked with one or two that just seemed to get colder and denser... maybe the Multigrade falls into that category now). Papers like Oriental and Kentmere require a rather strong solution. The Adox papers tone very rapidly in a very weak dilution of toner (so did the old Bergger NB papers). Slavich papers are somewhere in the middle. Hence my two solutions, one strong, one weak.
Maybe, if you find my methods valuable, you can pass them along to the many photographers you help with toning, etc.