This has gone on for some time without anyone asking what is meant by "mathematically equal"! I wonder if someone could explain that to me.
Feynman, years ago, gave an interesting interpretation of why all electrons are "physically" identical:
Electrons can be destroyed by contact with a positron and that is the only way an electron can be destroyed. Conversely, with high enough power, an electron-positron pair can be created. An electron can never be created with a corresponding positron. A positron is an anti-particle and, in a certain sense, appears to have "negative" energy. Feynman drew a chart with "time" as the vertical axis and a single space dimension as the horizontal axis and then drew a broken line running across that.
If you cover that with a "shield" having a thin horizontal window, representing our moment in time, and move it upward you get a picture of several "dot" moving left or write in the window. We can interpret that as an electron and positron moving toward or away from each other. As we reach a downward pointing corner in the broken line the two dots come together and disappear- an electron and positron destroying each other. As we reach an upward pointing corner, we see an electron-positron pair being created.
Now remove the shield and look at the broken line. If we think the electron initially moving from left to right, moving upward (forward in time), the "pair destruction", we see a corner and the line, representing the positron moving from right to left, now moves, still to the right but downward- back in time. That is a positron is actually an electron moving backward in time!
That's why all electrons are identical- there's really only one electron in the entire universe, bouncing back and forth in time!