Sorry, Darrel, but you're wrong.

Cantex manufactures both electrical PVC conduit, as well as various plumbing PVC pipes. They also do it just a few miles down the road from me.

The differences are:
"Electrical" PVC is rated for sunlight resistance, and has 'stiffeners' added for greater compressive strength. "Plumbing" pipe is generally assumed to be installed out of the sun (no need for sunlight resistance), and relies upon internal water pressure for some of it's strength.

"Electrical" PVC has not always been gray; when first introduced it was blue.

A more subtle difference is that the two categories are subject to different tests. While it is certainly possible for the same pipe to comply with both NEMA and NSF standards, there is little overlap between the standards; we simply can't say they comply without doing the tests.

Also left unaddressed by the 'they're the same' assertion is the difference in bend radius between the plumbing and electrical 90's.