I took a quick glance at the fares loaded in ExpertFlyer between London and Chicago on LH:
PNCGB1 LH P Round-Trip 3389.00(USD)
I assume you are referring to this fare, I see no SITI requirement.
I just want to inform you (pending travel policy and Ts&Cs) that for about $1,150 more you can go on LH in First via FRA on the B747-8i. I am booked on this in July, excited like a kid on Christmas.
ANCGB28W LH A Round-Trip 4550.00(USD)
Both fares require a Saturday night stay, but if you are Miles & More member the A class will give you 300% miles while P class only 100%.