One shouldn't throw around "Holy Grail" irresponsibly. Of course, that hasn't stopped anyone. If something potentially is a or, better, the grail, why could it be or is such?
Recently, I took a step back, and revisited the whats, whys and hows of (a) the problem statement Craig et al. formed and (b) the solution at which they arrived (which we now know is, mostly, PV-10). This exploration of mine led to a clearing where, triggered by reading several articles on cancer immunotherapy (such as this one) and tumor heterogeneity (such as this one), I thought I understood what I saw.
As I am wont to do, I very often ask management questions in hopes their answers will fill gaps in my understanding, drop knowledge on me and, as usually is the case, point me in new, inspired directions to learn more.
I think I now know one key aspect of why PV-10 is so unique (there appears to be another). I don't fully understand the biological science behind it, but I think I grasp its implications. Learning of it from different perspectives, starting with Craig's, the benefit of hindsight suggests the simple evocation: "Oh, yeah, that's it." But that statement, of course, does not do justice to the journey of the principals to arrive at that very point.
I will have more to say about this topic.