The "simplified assumptions" made by EZNEC (and NEC in general) are the
same ones you'll find in any circuit analysis or electromagnetics text.
EZNEC includes a model of a lumped inductor (or "load"), which is
accurately represented. It also includes an accurate model of a straight
conductor which has physical length. If you could build an antenna from
straight conductors and lumped inductors, the result would be very close
to EZNEC's predictions.

EZNEC does not have a model of a coil which has physical length. Neither
the straight wire model nor the lumped inductor model can or should be
expected to behave exactly like a coil which has physical length. As
I've mentioned before, a useful approximation can be made by inserting
one or more lumped inductor models into a model wire. I don't have any
measurements to assess the accuracy of that approximation, however.

Roy Lewallen, W7EL

Cecil Moore wrote:

The antenna current reported by EZNEC is inaccurate because of
simplified assumptions. EZNEC assumes that the current doesn't
change through the single point inductive load. Therefore, EZNEC
cannot be used to prove that the current doesn't change.