it looks more like a line
It is a line 
errorbars has no specific legend overload so it just shows the one for the underlying lines. One could build a better one in principle, for example:
f = Figure()
Legend(f[1, 1], [[
LineElement(linepoints = [Point2f(0.5, 0), Point2f(0.5, 1)]),
MarkerElement(points = [Point2f(0.5, 0), Point2f(0.5, 1)], marker = :hline, markersize = 10),
]], ["errorbar"])
f
