No it isn't. Take a photograph of a brick wall that fills the whole frame, using a good lens at F2.8 that's sharp from corner to corner. Take another photograph of the same wall and same field at F5.6, and compare DoF. Take a third photograph of the same brick wall at F11, but increase the size of the field so there are a few distant, rather blurry trees visible around the borders of the wall. Which image has the largest circles of confusion?
In order to have a meaningful comparison the elements compared must be within the most "tele" crop. The definition and use of CoC is already agreed, so lets not waste time on discussing this. The bottom line being that CoC can be used to decide DoF for any given photography irrespectively of aperture, field of view etc. The purpose is just that; to be able to decide DoF in a objective manner transparent from equipment. Its not a question about "Which image has the largest circles of confusion?", but up to the analyzer to choose an appropriate CoC and then compare with the same CoC across images to check DoF.
From Wiki and other sources “acceptable sharpness” in the final image (e.g., print, projection screen, or electronic display) is that the blur spot be indistinguishable from a point" and
"Visual acuity. For most people, the closest comfortable viewing distance, termed the near distance for distinct vision (Ray 2000, 52), is approximately 25 cm. At this distance, a person with good vision can usually distinguish an image resolution of 5 line pairs per millimeter (lp/mm), equivalent to a CoC of 0.2 mm in the final image.
Viewing conditions. If the final image is viewed at approximately 25 cm, a final-image CoC of 0.2 mm often is appropriate. A comfortable viewing distance is also one at which the angle of view is approximately 60° (Ray 2000, 52); at a distance of 25 cm, this corresponds to about 30 cm, approximately the diagonal of an 8″×10″ image. It often may be reasonable to assume that, for whole-image viewing, a final image larger than 8″×10″ will be viewed at a distance correspondingly greater than 25 cm, and for which a larger CoC may be acceptable; the original-image CoC is then the same as that determined from the standard final-image size and viewing distance. But if the larger final image will be viewed at the normal distance of 25 cm, a smaller original-image CoC will be needed to provide acceptable sharpness.
Enlargement from the original image to the final image. If there is no enlargement (e.g., a contact print of an 8×10 original image), the CoC for the original image is the same as that in the final image. But if, for example, the long dimension of a 35 mm original image is enlarged to 25 cm (10 inches), the enlargement is approximately 7×, and the CoC for the original image is 0.2 mm / 7, or 0.029 mm."
Imagine such a comparison. I produce on the one hand a lovely, A3 size print from the 400mm shot, showing the birds feathers, beak and eyes in sharp clarity. On the other hand, I produce an A3 size print from a very small crop resulting in a hugely interpolated print file that gives a very blurred impression of a few daubs of color that might be loosely interpreted as a semi-abstract rendition of a few leaves. The bird is not discernible.I say that, and further more they have the same perspective irrespectively of what you or I say!
What! Can't you see that these two images have the same perspective?
The "blurred impression of a few daubs of color" is simply due to that the small crop has been enlarged so much that details are lost. But the perspective will be exactly the same. You are mixing perspective with resolution. If you take your A3 print and aply the same resolution as to the small crop they will be identical. This is simply nothing to discuss unless you claim to change the laws of physics. If this is the case your results should be published elsewhere than here.