Honestly, I think the spelling of Eunsoo throws people who don't know any better about Korean pronunciation because of the way names like Eugene or Eustace are pronounced. They both have that 'Yoo' sound so if that's one's only reference point for how a name spelled like that should sound, it's gonna come out like 'Yoonsoo'. It's not at all an excuse for announcers who I'm pretty sure are given examples to follow at the major competitions (not that you'd know it from how some of them butcher names on the regular - I mean, even Tim Koleto was Tom this week so who knows what that female announcer had in her flask).
I wasn't trying to explain Korean to you or anything, so no offense meant! I was just trying to sort out why poor Eunsoo's name gets butchered so often. I speak five languages and the Korean vowels were the hardest for me to master (the grammar was a lot easier because I already knew Japanese when I started learning Korean and there were clearer parallels for me to grasp). Language and linguistics fascinate me so this may be off topic but I'm enjoying it, haha.