Background
This video on using an oscilloscope to view the line-to-line phase voltages of BLDC motors demonstrates the "virtual" ground necessary for such measurements. I understand this idea: you need to make a virtual ground for the probes because the oscilloscope's channels are all grounded to the same point (earth).
However, I don't understand the video's results in the context of an electric motor model: $$v_{applied}(t) = 2i_{phase}(t)R + e_{l-l}(t) = 2i_{phase}(t)R_{phase} + k_{e}\omega$$ Where the units of \$k_e\$ make sense (I think it should to be defined in E-RMS/(rad/s), but I've seen so many different definitions). Sufficed to say, back-EMF = func(speed).
Questions
Are the phase voltages seen in the video (snapshot below) equal to the voltage applied by the ESC (\$v_{ac}(t)\$)? Or are the measured voltages equal to the difference in the applied voltage minus the back-EMF (\$2i_{a}(t)R_{phase}\$)? Unless the virtual ground somehow negates the back-EMF, I don't see how these voltage measurements don't also include back-EMF.
Heck, I'm even more confused now about the sensorless speed control programs used in hobby ESCs: how do hobby ESCs measure back-EMF? If an ESC only energizes 2 phases at once (say, A is HI, B is LO) and measures EMF on the third phase (C), then why does the back EMF on phase C matter if it doesn't affect Vab?