I think you will find that most modern cultivated edible figs are self
fertile.
doesn't that just mean that the wasps can just use fruit on the same tree;
they don't need to flit from tree to tree?

Technically, yes, when speaking of other types of fruits like apples or
cherries. Actually, most of the cultivated edible figs do not require
pollination at all in order to ripen. They are either self pollinating or
apomictic (parthenogenetic). The only cultivated figs requiring wasps are
Smyrna figs.
The little green balls on the Green Island fig, unless they are self
pollinating, will probably grow to a certain point and then fall off. It is
difficult to tell exactly what is happening with a fig, since the flowers are
on the inside. You might find it interesting to cut one in half. Remember, the
little figlet is not one flower; it is a whole inflorescence.
Iris,
Central NY, Zone 5a, Sunset Zone 40
"If we see light at the end of the tunnel, It's the light of the oncoming
train."
Robert Lowell (1917-1977)