Is a pvc bend radius ever so large that it no longer counts as a bend? I'm referringto buried pvc that may have a gradual curve. To exaggerate, consider a pipe that eventually turns 180 degrees but takes 500' to do it.

The example may be considered a very large elongated sweep.

Seriously, IMHO a short answer is no!

I've seen gigantic bend radii in underground phone conduit.
The short answer is that a 90 degree bend is a 90 degree bend.

A lot of Cables including HV have required bending Radius ,
Thus long radius 90's.