This is a quiet acknowledgement by Oda that Franky's design was better pre-timeskip. The hairstyle is back to classic, and the round shoulders are nowhere to be seen in the 70 year old version.
Good end Franky is horrible. It lacks any and all sorts of romance and manliness. Post timeskip New World Second Half Yonko saga Franky is pure soul. Franky ending up as a battleship should be the ideal future.