ENSO might not be as connected as you think.
If you focus on the coldest normal equilateral region in the Pacific Ocean, which perfectly fits Strongest Nino's.. minus that signal, and you can see there is a weak PDO correlation. More west-based events have a higher PDO correlation because of the Hadley Cell/mid latitude Cell feedback at that longitude. But the "pure" Nina/Nino's, which are based on the coolest equilateral SST region, actually only have about a 0.30-0.40 PDO correlation.