This morning, the seed leaves had opened up as I had expected, but there were three instead of four. It turns out that there may be anywhere from three to six, with four being the most common. Looks like this little guy is special! The National Park Service has a great page on Giant Sequoia development if you're interested.
By nighttime, the stem had straightened out a bit more, as the seed leaves started pointing upward. I should start to see secondary leaves in about 2 weeks.