I've used my Flex-5000a in FMTs and its last digit IS
spot on, especially when the radio is calibrated using the built-in Flex method which takes just a few seconds. To estimate to 0.1 Hz I use the Flex's scope. Doppler and other factors complicate things. And just hearing all FMT beacons can be difficult. Flex radios are very popular in FMTs.
I see your results which are excellent. Two of your three readings were within 1/2 Hz. http://www.b4h.net/fmt/fmtresults201404.php
Some older radios give the software option to turn on an additional digit on the readout. I think my old TS-850 and TS-440 can do that. But that digit is pretty close to random. Fifty years ago, the one-KILO-Hertz Collins readout was remarkable. Now one Hz accuracy is common for new models.
Are the $10,000 rigs better in this regard that the $2k to 3K radios?
I think $600 Flex-1500s and some other SDRs may be on the mark. Elecraft K3s are good to about 1 Hz. I'm reading that stock Anan SDRs aren't terribly accurate. How good is the new Flex 6XXX series? Those FMT Scores suggest it's no better than old Flex radios.
You get better with FMTs with practice. Join the Yahoo FMT group.