Assuming you are booked on the QF flight number (rather than a codeshare) it doesn't. If you want to sit upstairs then give Qantas a call directly and request a seat on the upper deck and if there are any available, you can get them. The only blocked seats upstairs will be those in the exit row

As mentioned by #6, there is a max allocation limit before they stop allocating seats to non status FF members, but as long as that hasn't been reached , then in business, you should be able to select from nearly any seat available ( other than exit row 16 )

In economy, the 1st few rows are limited for preassignment to those with OW status

Dave