Here are my pics of the Prismatic Hi-Power Cells I took apart. There is NO vent. Just an o-ring around the removable cap. No room for flooded electrolyte either. There was so little it makes no difference which way you orient the cells. It has been recommended to NOT put them upside down with the vent on the bottom. The area around the terminals is not sealed and electrolyte could leak out from there. Its tight but not sealed.
Stand them up, lay them down or on edge. No problem. No, they are not swimming in electrolyte.