In energy terms, I guess the difference is that this is harvesting energy from a variety of signals, whereas a passive UHF RFID tag is designed to harvest energy only from the very specific frequency of the energising pulse, but the physics must be the similar.
In data terms, there is more going on when reading UHF RFID tags than just a simple 'chirp', but it's definitely not general purpose computing like this.
PS: "The RF in RFID" by Dobkin is an excellent book.
The RF in RFID: Passive UHF RFID in Practice https://www.amazon.co.uk/dp/0750682094/ref=cm_sw_r_cp_apa_i_JvMqCb8RXHFCE
Not that I know of. There was a 2007 book by the same author, but it was directed towards UHF RFID.