Originally Posted by Majuki

Your coworker wouldn't be able to access the Sakura Lounge with the AmEx. You can check which clubs you can access on an AmEx Platinum with the link you provided. With the AmEx you can only access true Admirals Clubs, not partner lounges.

Also, the Sakura lounge is after passport control but before security for AA 71. The security checkpoint is right outside the Sakura lounge entrance, and there usually isn't much of a wait.

I'll agree with the other comments that you're not missing much with this lounge. There isn't much space, and the food offerings - at least in the morning - left much to be desired.