What is a substantial reason to travel on a bridging visa BVB?

I've been on an Australian bridging visa A for nearly a year now. Until Christmas last year I didn't have the need to leave the country yet. And so far I was very happy with my bridging visa, as it allows me to work full-time and study full-time and so I'm not limited to anything apart from travelling overseas. 

Bridging Visa BVB

If you do need to leave the country you have to apply for a bridging visa that allows you to travel. The bridging visa B allows you to leave and return to Australia whilst your substantive visa application is being processed. You have to re-apply for the same bridging visa you were on before when you return to Australia.

The reason you have to go through this effort is for the department of Immigration to know if they can communicate with you whilst you are away and for them to know what is happening with you and where you are. Which makes sense from their point of view.

I've applied for my de-facto partner visa last year in April. So it's almost been 10 months now. When I applied for the visa I got a confirmation letter saying the average processing time for the visa is 13 months. That's the point I accepted the wait and I knew there was nothing else I could do than just WAIT.

Substantial reason to travel
When I decided to leave to The Netherlands with Christmas, my ticket was already booked,  when I realised that I had to get my bridging visa approved before leaving the country. However the department of Immigration gets really busy around this time of the year, because everyone wants to leave the country. I started stressing as I thought: ,,Is leaving the country to spend Christmas with my family a substantial reason to leave and return.''

I found out 7 days before leaving that it indeed was a valid reason. This year in April I have to leave the country again for the wedding of my sister. So I called the department yesterday asking if weddings are a substantial reason. The answer was ,,as long as you are not a criminal you will be fine to leave the country and return'' I thought, really? This is what I've been worrying about all the time. ,,You do always have to fill out the form notifying the department of the reason you leave.''

Useful to know: You should apply for a Bridging visa BVB no more than three months before, and not less than two weeks before you want to travel. You don't want to risk it to not have an approved Bridging visa BVB, because without this visa granted you won't be able to return to Australia.