Weird. My wget gives full resolution. No redirect options or anything. Only difference is the IP resolve for you is in Korea and mine is in the US. Likely just closest server resolve.

Try curl with -L set?

Or I'd be curious if something like gallery-dl resolves the image in finding the higher resolution and what the difference is if it does.

Maybe it's a DNS issue if not a redirect issue.

My guess is DNS. Try with another provider?