Hello Hrishi,
LSE is Local Space Euclidean coordinate system. Its orthogonal (Cartesian) system which doesn't consider any corrections related to the Earth curvature and etc.
Multiplication by (1, -1, -1, 1) diagonal matrix is required to switch from Metashape coordinate system orientation convention to another one required to estimate exterior orientation parameters in geographic/projected coordinate system.
In classical camera coordinate system rotation angles are defined around the following axes:
X axis is directed to the right of the image,
Y axis is directed to the top
and Z axis - backward. Whereas in Metashape in camera coordinate system Z is pointing to the camera view direction.