This isn't accurate, like most invocations of electrons when trying to explain electricity. Ignore the electrons, focus on the fields, where the fields go the electrons will (try to) follow.

Ethernet doesn't even have "ends", really. A compliant 10baseT connection is two loops, one in each direction, with a small transformer at either end. Because it is impossible to transmit a DC level through a transformer, all you can actually transmit are edges, which at that frequency get rounded off nicely. That's why it has to be DC-free, because only pulses count. There's a substantial level of DC isolation between the ends, something like 1.5kV.

(100baseTX is slightly more complicated but still has the same nonzero constraints https://en.wikipedia.org/wiki/MLT-3_encoding )

Andditional reason why you should ignore the electrons: they will simply confuse you when reasoning about transmission lines, as the signal velocity is much faster than the electron drift velocity. If you look very closely and ask questions like "why does the signal velocity depend on what the dielectric is?" you realize that the signal isn't "in" the wires, it's "in" the space between them, which is an insulator, and therefore not dependent on electrons at all.