That does seem to be the case. Clay Harmon notes that TMY and FP4 require roughly equal development times throughout the SBR range to achieve a density suitable for palladium. That is at the 1.5:3:100 dilution. I will probably just start by trying FP4 at the same times I have been using successfully for TMY with the 2:2:100 dilution.
I do not have a densitometer or the means to do BTZS testing, but I find the metering techniques easy to use so I borrow other people's numbers and adjust them for my own use. I realize that is probably is a violation of the rigorous principles of the BTZS technique, but so be it.