It's potion time!
The only reasonable explanation for ever considering that episode as things to come is if it turns out Dratini will be added to the games and it comes with a Gigantamax form.But, the tournament we're talking about isn't a random 'Whirl Islands Cup' or 'Battle Don's Tournament'. It is as established as the Battle Frontier and one of the main features of BW2. The episode, also, clearly states it is between two Champions.
I mean — I couldn't be the only one asking for PWT when Galar was announced from the start. Personally, it is a positive sign that the tournament is acknowledged and happening in Galar, which could have been used to promote the Unova episode.