When you construct a wall, you want to have a bottom plate and a top plate. Basically, you cut or order all your 2x4s to be the same size and simply nail them to another 2X4 on top and below to make the wall....then lift it in place and nail it to the floor....and build up....from the top plate, you can attach trusses or beams. In this case, being a basement, they likely have that beam resting on block or concrete walls....added the steel post to keep it from sagging. Because there's no top plate on the wall, you can tell they just built the wall in place around the post. Having said that, it would still bear a load if the beam ever sags and provides a place to hold insulation. Just make sure you don't have moisture coming through any of those walls if you decide to close them up. It's not uncommon for moisture to float through walls and cause mold. It's worth sealing and addressing properly.