I have the wiring configuration for a RHEEM thermostat Pictured Below. On it, there is a "V" wiring connection which according to the manufacturer is for "Pulsed width modulation" type heating. On the other end, the furnace, it connects to a "V/W2" connection which I have verified is pulsed width modulating.
Initially, Nest showed that I was incompatible due to the "V" wiring but learned that it was because they thought it was "milivolt" designation. However, after talking with them and researching, I learned that this was not the case and should be able to connect the V/W2 into the Nest "W2".
Will this accomplish the same thing? I learned that W2 is for 2nd stage heating which doesn't seem to be exactly the same thing as Pulsed Width Modulating heating.
Edit – Found in manual:
From Manual
To set the furnace for operation with two-stage thermostats, set
switches 1 & 2 of SW2 to the “ON” position (See Figure 56). Note that
these switches should be in the “OFF” position from the factory. With
both switches in the “ON” position, the furnace can still recognize a
“V” signal present and will still operate with a modulating
thermostat. However, with both switches of SW2 in the “ON” position,
the furnace is set to operate with a two-stage thermostat as well.
With a two-stage thermostat (installed as shown in Figure 50) and
switch settings configured as described above, during a call for heat,
the furnace will operate as follows:
So it is currently operating in "modulating" thermostat mode but is able to operate with Nest in a "2-stage" mode by simply flipping a dip switch. Then the "V" wire will act as "W2" wire.
Best Answer
It looks like this type of heat is called "modulating heat" or a "modulating furnace". I can't find any information saying that Nest supports that.
The labels on the thermostat and furnace are meant to be a convenience for the installer, and you really have to refer to the equipment documentation to see what it does. The common labels of R, G, Y, W, C are fairly standard, but once you go beyond that, there are conventions, but you have to research to know the exact use of R, W2, B, etc.
That's a long way of saying that just because the furnace happens to have a W2 label and the Nest also has a W2 label doesn't mean very much. You have to dig into the documentation (as you have done).