as always 5 seconds after posting. lay the monitor flat in its foam tray with base attached. then push really firmly forward on the opposite side of the base. It is just really stuck. the screw plays no role.
On the back of the monitor case, where the base leg input connects to the monitor case is a swivel joint high on one side low on the other.
The joint has grooves that should allow it to move the face of the monitor from leaned back to vertical. The swivel joint does not move. The monitor is stuck leaned back when placed in a normal position standing on its base on a desk. On the back of the monitor case one inch above the swivel joint is a silver screw that appears to be related to the unrelated VESA mount. The VESA mount is not being used. I am using the stock monitor base on a flat desk.
There is otherwise no sign the screw is related to the swivel joint. The screw loose or tight does not change the swivel joints ability to move. The monitor stands leaned back 10 degrees. And of course Samsung customer support was no help, nor does the manual address anything but base assembly, tab into slot b, and not to bathe with it.