You're both right. Biochemical recurrence (BCR) is officially
defined as a confirmed rising PSA over 0.2 after prostatectomy. But that does not mean that it is a good idea to wait for a BCR before salvage radiation is offered to men with adverse pathology - it almost certainly would be a bad idea to wait that long. That's why the evidence strength is grade C.
In fact, what the AUA/ASTRO recommends for men with adverse pathology, like refers, is:
Patients with adverse pathologic findings, including seminal vesicle invasion, positive surgical margins, and extraprostatic extension, should be informed that adjuvant radiotherapy, compared with radical prostatectomy only, reduces the risk of biochemical prostate-specific antigen (PSA) recurrence, local recurrence, and clinical progression of cancer...
Physicians should offer* adjuvant radiotherapy to patients with adverse pathologic findings at prostatectomy, including seminal vesicle invasion, positive surgical margins, or extraprostatic extension, because of demonstrated reductions in biochemical recurrence, local recurrence, and clinical progression.
So AUA/ASTRO advocates immediate radiation in cases like refers, so as to prevent
BCR. They are not
recommending waiting for BCR. The problem with their recommendation is the risk of overtreatment -- there are many men with adverse pathology who will never go on to have a full-blown BCR. To prevent overtreatment, doctors are looking for a uPSA that is high enough to prevent overtreatment with adjuvant RT, yet low enough so that outcomes are not appreciably different from ART. 0.03 seems to be the Goldilocks number - in men with adverse pathology, it reliably predicts BCR. And in adverse pathology men, uPSA less than 0.03 does not reliably predict BCR. They call this "early salvage;" it seems to be the safe middle ground between ART and SRT.