I think, on the whole, that you're right, but like so much else, depends who's doing it, and on what. Depending on setup and stringing, as well as technique, I imagine it's possible to get pretty close with an electric, but uncommon to 'not hear the difference'.
If you go back to the earliest days, when even the amplified electric was not that much louder than an upright, then it was probably a great deal easier to not know the difference on pure listening. This test has been done. Take a 52 P-bass, set up and strung as in 1952, an original 26 watt Bassman, set on medium volume, play with thumb. "...the loudest upright you ever heard!"
Today's instruments and, particularly, amplification, don't really allow it to get that close any more, without serious effort, that is.
That's my take on it.