I had already 3 phone conversations and 2 email exchanges with avis on the same topic. The answers are usually that international does not count but whomever I get can't really state where this is written.
From my 7 rentals in Zurich 3 show as qualified and 4 don't. The 3 that did not quality were prepaid rentals via the avis web site, the 4th shows 'minimum number of days not met' and this was an 8 day rental.
I think Avis phone and e-mail customer service is abysmal bad and it seems random whether they count international or not. All my national rentals did count though with no problems and I already hit the 10 rentals easily in any case so I did not press the issue.