aristoph you need a little terminology here. The One World tickets are:

One World Explorer ticket a/k/a OWE = fare depends on number of continents visited
One World Global Explorer a/k/a GLOBEX = fare depends on mileage
One World Circle Indian Ocean a/k/a CIRIND = as it is described, can circle the Indian Ocean, i.e. travel to Africa, South West Pacific (Australia in your case) and Asia possible. European originations are permitted.

There is no such thing as a Circle Trip Explorer Ticket. The folks here are suggesting the relative merits of OWE vs. GLOBEX vs. CIRIND. You can find the rules for them here if you want to read up yourself. Good luck with the planning.