An hour and a half would fly by in the theaters, and Marvel Studios would likely want to milk the team up of Hulk and Thor a bit more than that specific runtime.
Additionally, Waititi made a joke about 40 minutes of the film being credits, so it puts his response to the rumor into question.
Because 90 minutes actually feels a bit short for a film that is so out of this world and features so many iconic characters.
It’s debatable that 2 hour and 10 minutes was a bit too long for Thor: Ragnarok’s length, but the film’s director may not be telling the whole truth in regards to his response.