There's been at least one post questioning Poncirus+ winter hardiness. Due to experiencing a very mild winter, I can't really address it's ultimate winter hardiness, except noticing that they're the only trees showing bud-break this early. None of the citranges, other Poncirus, TaiTri, 5* citrumelo, Ichangquat, etc. are showing bud-break. Perhaps this early loss of dormancy contributes to decreased hardiness.
It remains to be seen whether the remainder of the selections will follow within days, or will remain dormant for several additional weeks.