In terms of GPU upgrade priority to Polaris, do I understand correctly that even a low-cost premium economy fare has
higher priority than any regular economy fare? I am looking at booking flights to Europe in R (lowest PE fare bucket) and applying (waitlisted) GPUs to try to get Polaris. The R fare costs about the same as a W fare--and, if I'm understanding correctly, has higher priority for the upgrade while also insuring against the downside risk of remaining stuck in E.
(Maybe this has already been addressed/confirmed above but my attempt to search didn't find it.)