Ahhh, the test was devised in the heyday of B&W, back in the 40s IIRC or maybe earlier. And, it is still used today. The KI test is very sensitive due to the very low solubilty of AgI and the high color of pure AgI. So...
If you follow the Kodak instructions, or those on the Formulary kit and the hypo passes, and then test for washing with hypo and silver retention kits and the paper passes, FB paper is just fine.
It's all long winded testing like that, just following good sound practice & two bath fixing makes life simpler, and gives better economy. I'd rather test the old first fix bath & know that the fresh fix is removing any residual silver/thiosulphate complexes.
Oh, I agree Ian. The only reason I posted the KI test is that some of the strip test kits related to what you mentioned earlier are just strips of KI in a blotter like tab on plastic. Same things. Different method of use.