A few observations:
1) Your average digital potentiometer on a chip will only work to the chip supply voltage, feed anything more than this and you let the magic smoke out.
2) Your average digital potentiometer on a chip is a low current device, this method could be used with a wirewound resistor in medium current applications.
3) Most digital potentiometers use either I2C or SPI which means a microchip somewhere, this technique could use a simple 555 chip.
4) Isolation between the control signals and the variable resistor is very good, useful for high voltage applications.
So, this particular implementation may not be too neat but the idea is sound,