Update affine.rst

Please mention these important points somewhere on the page.

Proof:
```
$ echo 0 0 | proj +proj=affine
Rel. 9.3.0, September 1st, 2023
<proj>: 
can't initialize operations that take non-angular input coordinates
program abnormally terminated

(Actually as a second +step of a pipeline proj still accepts it.)

proof of units:
$ echo 0 1 | cs2cs +proj=affine +xoff=1
57d17'44.806"W  57d17'44.806"N 0.000
```

docs/source/operations/transformations/affine.rst

@@ -20,7 +20,7 @@ x,y,z coordinates, and translation and scaling on the temporal coordinate.
 +---------------------+----------------------------------------------------------+
 
 By default, the parameters are set for an identity transforms. The transformation
-is reversible unless the determinant of the sji matrix is 0, or `tscale` is 0
+is reversible unless the determinant of the sji matrix is 0, or `tscale` is 0.
 
 This can be used to implement:
 
@@ -47,7 +47,9 @@ This can be used to implement:
       source CRS to obtain the correct scale of the target CRS.
     * :math:`\theta` is the angle about which the axes of the source CRS need to
       be rotated to coincide with the axes of the target CRS, counter-clockwise
-      being positive
+      being positive.
+
+Note: +proj=affine cannot be used with the proj untility. Input is in radians, output is in degrees.
 
 Parameters
 ################################################################################