This was a fascinating read if for no other reason than seeing how the filters were assembled. I have much more understanding of digital than analog, to say nothing of RF stuff.
I would love to see more stuff like this that is so understandable! Makes it seem much less like black magic...
Yes, it's a nifty technique. One detail that might not be immediately apparent is that it drives the LC circuit in a series-resonant configuration, where it looks like a low-impedance load that can accept a lot of current from the transistor half-bridge, but it receives the response in a parallel-resonant configuration, which is good for sensitivity when driving high-impedance loads like the 22K input resistance presented by the opamp circuit.
For this topology, best results will depend on low-impedance AC bypassing on the Vcc line, which he doesn't show on the schematic. I'm sure the Arduino's supply input has enough capacitance to take care of that, but if you adapt the circuit to other uses it's something to keep in mind.
I would love to see more stuff like this that is so understandable! Makes it seem much less like black magic...