Hmmm well that's a very interesting theory, because that's exactly what the Dicodes does. With the Dicodes, you have to tell it to lock the resistance - similar principle to Set Resistance on a Yihi.
When you do that, it probes the coil with a small voltage, which I believe is a fixed amount such that it pushes different coil types up by varying amounts of temp. I haven't been able to see how much voltage applies because it's so fast it just causes my DMM screen to flash without displaying a figure.
But I can see it on the Dicodes screen - after probing the coil it shows the temperature as >20°C for a minute or so until it settles back to 20°C (the Dicodes assumes all coils are 20°C as it has no internal thermometer.) And more importantly I can see it on my external temperature sensor.
So could the Joyetech being doing the same? Absolutely. But if it is and isn't then refining away the difference, or simply showing the locked base resistance pre-probe, then that's.. odd. Of course it might simply be a display bug, and it locks at 0.34Ω, probes it up to 0.37Ω, displays 0.37Ω, but keeps using 0.34Ω.
I still don't understand why my Dicodes even does this probe. It's not mentioned in the manual or their separate Application Guide for Temp Control Vaping, which is otherwise rather detailed on their methods. I don't quite see what it achieves.
Anyway, assuming you put the coil on at 20°C, a 0.34Ω Titanium coil heated to 0.37°C has increased in temp to 45.21°C. That's in the right ballpark for where the Dicodes often heats coils to - at least Ni200, which can go as high as 60°C according to the temp probe. Titanium coils heat less. Not that that means anything, if the Joyetech is applying a small voltage it won't be exactly the same as the Dicodes.
So yeah, your theory is a good one. If correct it's still weird that it shows the post-probe resistance, but that could be a simple display bug.
When does the VT detect resistance? Do you have to press a button, or is it auto once you've screwed on the coil? If you have to press any button, then you could probably detect the voltage if you have any kind of DMM or volt meter. Connect it to the atty posts with crocodile clips and then press the button. On mine all I see is the scale at the bottom flash (the visual graph thing that's gives a bar-graph type display of the signal), I never see a figure, but before I got my temp probe it was enough to verify that there was a voltage being applied.
I was thinking of ordering a VT today but I might wait till early next week to get one a bit cheaper without the tank. As soon as I get it I'll be able to tell immediately on the temp probe.