The trouble with IMDB when used internationally is it shows information pertinent to where that specific user logged in from, so we're unlikely to see the exact same information you do.
I see two formats, 1.90:1 IMAX & 2.35:1. Neither is 16:9 and both would have to be cropped to 16.9, one vertically , the other horizontally [or post-boxed/letter-boxed]. Without knowing which of the cinema formats used the most of the frame, you'll never know which is the 'best' crop to 16:9. The original cinema format is almost never 16:9. If shot 35mm, most likely they cropped both out of the original film frame [3:2], at different aspect ratios. Neither is more 'correct' than the other.
When downloading/streaming, the metadata will only show the presentation format of the encapsulated movie, it cannot know whether it's been cropped, post-boxed or letter-boxed to fit into that format.
To be more specific on "How to find the aspect ratio at which the movie was shot?" You'll never know unless you find documentary evidence from the director etc. Even knowing what camera &/or film stock was used will not tell you exactly how the framing inside it was set up.
See: How are some scenes for movies shot especially for iPhone viewing?