Needles in bundles of 2. If you treat it like a single flush 2 needle pine, you won't kill it. Even the double flush pines like JBP, will not be harmed if treated like a single flush pine.
This is proof you got $0.75 worth of seed, definitely not Japanese white pine. The same quantity of JWP seed from a reputable company with brick and mortar headquarters and a real address would have cost $5, and every seedling would have been JWP, you would not have had to ask for identification.
It is fun to have the occasional mystery. But until one of your seedlings matures to produce a pine cone and pollen cones, yo will not be able to to say with certainty that these are one species or another.
Most likely the Chinese race of Japanese black pine. But they could be Japanese red pine or one of the other 2 needle pines found in the Chinese landscape. They have at least 6 or more 2 needle pine species native to China, in addition, introduced species like Pinus sylvestris are possible. Good luck sorting it out.