P: Fit Image "do not enlarge" - still enlarges picture size

I have a problem with the 'fit image' via file automate which seems to be a bug as you can reproduce this with any image:

Take a file e.g.. 5758x3728 pixels width/heigh.
Go via 'file - Automate -> fit image

Give e.g.. pixelssize 6000x6000 + tick Do NOT enlarge.

The image still enlarges the file to 6000 pixels.
Even though I have selected do NOT enlarge.

This happens with every image I try and which should NOT be enlarged.