That is inaccurate, they cannot access the IFL. Also, flying SQ F as others have mentioned gives access to the VS Clubhouse, terrific lounge, great bar area and food to order. You would also be able to access the SWISS First Lounge as well.

VS is one of the nicest lounges at JFK. You must have flown out of IAD on LH in F, which also gives you access to the VS clubhouse there. LH C class out of IAD access the NW Worldclub.