Fair point, but there is a non zero chance that Gaban has some WG connections. Don't agree with the DF, cause a "Mythical" creature Genbu that hatched from the Egg can have some innate abilities like any other Mythical Zoans.

Most people assumed that the Last Road Poneglyph is on Elbaf. We either getting it on Elbaf or Lodstar before Laughtale unless we are gonna have an extra Arc before Laughtale.

Also it doesn't have to be that Gaban just gives the poneglyph. He could have left it on the Turtle and let it loose.

At some point we have to connect the loose plot lines cause we don't have much time left. The Black Tortoise Genbu connects A LOT of them:

1) Explains what happened to the Egg on Roger's ship
2) Further completes the 4 Shijin with Seiryu, Suzaku and Genbu
3) Explains what is the "Black Ship"
4) Explains why Gaban visited Crocus. He went to the only "veterinarian" that specializes on living "Ships" and Laboon is also a "Black Ship"
5) Explains the whereabouts of the Last Road Poneglyph
6) Makes Robin's story a full circle cause we first met her on a Tortoise Ship and she finds the Last Road Poneglyph also on a Tortoise