Garzetti must have some basis for
his assertion, but I cannot find what it might be!
Nothing in Dio or Suetonius about a refoundation of
Rome in 73. Nothing in the Critical Notes to the Garzetti book you quote,
nor in Bengston's The Flavians or
his Summary of
Roman History,
nor in Homo's lengthy biography of
Vespasian, at least that I could find in a quick perusal.
Probably the "refoundation" is just a modern conjecture, connected with Vespasian's assumption of the censorship in 73.