Any value added to the right-hand column of cammat4 will be in normalised units, i.e. 1 unit is half the width/height of the window.
If you want to move in “user” units (i.e. the coordinate system used for left/right/bottom/top), you need to multiply the orthographic projection matrix by a translation matrix, and use the result as the MVP matrix.
I am now translating the camera by the velocity of the player.
However, nothing seems to have changed, no need to show another GIF, as there is no difference, it’s still using normalized units.