The confusion is a translation issue. Here's the actual language from the magazine:
It says "earned 1,000,000 miles or more on KoreanAir
and/or other SkyTeam partner airlines."
Taken at face value it seems to suggest that you are part of the club if you have earned 1M from a SkyTeam partner airline but I'm guessing the intent is those with a million miles on a SkyTeam partner
who have credited those flights to KE are part of the Million Miler Club (the same way partner travel historically has counted for UA / AA / DL though there has been change on that front in recent years).
It's not saying that SkyTeam partner Million Milers are part of the
KE Million Miler Club and have the related benefits including access to the lounge.
Per the article linked above the requirements are pretty stringent even if you are a KE Million Miler:
Korean Air's Miler Club Lounge is reserved exclusively for the following passengers:
- Korean Air Morning Calm Premium members travelling on a KE flight number in business class or first class.
- Korean Air Million Miler Club frequent flyers, also when travelling on a KE flight number in business class or first class.
A Morning Calm Premium or Million Miler Club card on its own won't get you into this lounge, nor will a business class boarding pass: you'll need to have
both.