P1 Grand Prix Fighting Tournament

[TeamRocketDude]

In the article for the P1 Grand Prix fighting tournament where Ash wins with his Primeape, the article says that the tournament takes place in Celadon City. The episode itself doesn't specify, but Ash seemed to have left Celadon after beating Erica, so if it is indeed Celadon, he must have doubled back. In liu of any other evidence, I'd think it would make more sense that the fighting tournament was somewhere on Route 16.

Pokemon.com states that the episode takes place on the outskirts of Fuschia, but that doesn't quite make sense either, as it is quite a few episodes of travelling before Ash challenges Koga.

The bulbapedia article states that Pokemon.com is incorrect, and the article has a poster with Hitmonlee throwing a kick. This poster is very interesting. It states that the Tournament is sponsored by Silph Co and does take place in Celadon. What is the origin of this poster? I can't find it anywhere else. A reverse image search only leads back to Bulbapedia. Supposedly it is from the Japanese Game Freak site in 2014, but I can't find any supporting evidence of this?

I'd love to know if this Hitmonlee poster is official Game Freak info, because for all I know it could be fan made?