In 1982 & 1983, there were two releases of G.I. Joe series. We had, which are the original series, the “Straight-Arm” followed by the “New Swivel Arm Battle Grip”.
The Straight Arm series were labelled so because even though the arms could bend at the elbow, they were unable to move through the shoulder.
As you’d probably assume from the second name, their design was updated to have more movement in the arms but have a new waist piece as well!