"art"
There you go again, "may" does not affirm fact.
_________

OK, then.

A 1/2-wave dipole absolutely HAS more directivity than an isotropic radiator
(and so does every other practical antenna).

But when any/all of them accept the same amount of power from an r-f source,
then they ALL will radiate the same total amount of power.

So they are all equally efficient, by the classic definition of total power
in vs. total power out.

Antenna directivity/gain is not a measure of efficiency.

RF