I've been thinking about this very issue lately as well.
I'm hoping some of the fixer experts (PE, et al.) chime in here. I have doubts about the higher capacity claims as well. And, while we're at it, we might as well drag the Ilford archival sequence into the discussion. Lots of fodder here for an interesting thread. I'm looking forward to it.
FWIW, I don't have an issue with washing longer, which I usually do, and I do residual hypo and silver tests (HT-2 and ST-1) to make sure my work-flow is not grossly out of whack, but I haven't taken the process to the limits in years, and certainly not with an alkaline fix like TF-4 or TF-5.