Well I agree with you here totally, but this was not the case. It was Boston to Sydney in F. I've verified their "international surcharge" calculation on ITA matrix and it is correct.

For flights within US, carrier surcharges don't exist, except $2.50 per leg. So thats $10 per round trip, maximum ( 2 legs each was for one region award are allowed)

I am still awaiting to hear from SEN desk, because they escalated the issue to the main office in NY. They've agreed over the phone that something is odd and worthwhile checking.

At the very best I am expecting them to fix their award charts and remove this vague language.