I know its might not be relevant for you. I send an email to mark he is a registered migration agent then he replied.
"I can't comment on your eligibility without seeing your documentation at a consultation, however generally speaking the there is a policy allowance of 3 weeks per year for an applicant to be outside Australia on vacation, etc while still maintaining a residence in Australia, and the 3 weeks per year is not deducted from the living in Australia time - ie, it's counted as time in Australia for purposes of the requirement of the 887 visa to live in the designated area for 2 years while holding the 489.
I have no idea is it legit or not, probably no one can say anything about it. Best of luck once again.