I probably should've guessed what the question would be.
These new modified rods were designed for Gordon to recreate the eccentric rods near his middle driving wheels:

Percy's connect to his valve gear from the rear:

(Both screenshots from the TTTE Wikia).
As you said, the 2015 Gordon rods would look wrong on Percy without an extra piece joining the ends diagonally:

Super wrote
Speaking of these special rods...off the top of my head I can only picture 2 trains that have unique side rods...this one from the Newer Plarail Gordon and the Plarail or Trackmaster Dennis. Are there any others???
Edward (original)
Oliver (similar to Edward's, but with thicker grooves)
Henry (original)/Gordon (original)/Hiro (TrackMaster 1)
Harvey (original)
Emily (original)
Stephen (TrackMaster 1/Plarail)