That's in line with my general thoughts too, Token. My main HF antenna has been down for a few months, so online SDR's are my only choice. However, even when it was up, I am in a fairly noisy and less than ideal urban location. The KPH SDR is in roughly the same part of the world as me, so represents close to what I could hear if I had a better location and good antenna.
My thinking is that a reception report, whether from a local receiver, or online SDR, is a data point and, as such, is potentially useful. Important, as you say, to note the location of any online SDR being used.