Why not just go around Cape Horn? It takes longer clearly but is it better than waiting? My guess is fuel costs for one and maybe weather issues? Are there other reasons?
Typical losses with LNG are about 0.1-0.15% per day depending on the type of carrier. A round trip around the cape would add probably 20-25 days or so for a typical ship. More for slower ones. So, the price of that is 2-3% losses. The value of LNG fluctuates wildly in recent years. But it's not cheap. At the peak, a single ship could be carrying hundreds of millions $ worth of LNG. So, a few percent losses is quite significant.
Not to mention that there are fairly steep piloting fees for the Magellan strait. I wonder if USN carriers take on pilots when they navigate it or if they have a political exemption.