GIMP 2.10.20 (revision 1)
Paste as Image - wrong dimensions (bug?)
Select 3500 x 4500
Paste as Image
New Image = 3522 x 4500
To test this
I created a new image at 3500 x 4500
Then pasted into selection
This time, there was a gap at the bottom of the image - the checkerboard was visible.
The image appeared to have shrunk to the width, and therefore shrunk the height.
Either way, the selection size was clearly 3500 x 4500 yet it will not paste at those dimensions.
Paste as Image - wrong dimensions (bug?)
Select 3500 x 4500
Paste as Image
New Image = 3522 x 4500
To test this
I created a new image at 3500 x 4500
Then pasted into selection
This time, there was a gap at the bottom of the image - the checkerboard was visible.
The image appeared to have shrunk to the width, and therefore shrunk the height.
Either way, the selection size was clearly 3500 x 4500 yet it will not paste at those dimensions.