I know you're joking, but genuinely I make no secret of the fact I think I was very fortunate to get my promotion when I did. I must have just about scraped an invite to an assessment day (which without my last planned observation being postponed I may have either been more comfortable or may have missed out) and then at the assessment day, passing the fitness test proved to be half the battle (although once again, passing the fitness test itself is no matter of luck, but I was a little shocked by the number of candidates that failed it).
If you looked at my observation marks immediately after my promotion also, you would think that I am someone who has been found out and is heading back towards reclassification, but fortunately you get half a season (or a season, depending) grace and this season has started a lot more positive.
There are definitely elements of luck, but you still need to be good enough also. There are certain things you can control. Refereeing isn't all about running, and sometimes I run unnecessarily, but in 4 assessments since getting my L3, I've been marked 8.0 for section 4.1 (work rate / movement) 3 times. The other time was the day after my best mate's wedding where I was best man and in all honesty I probably shouldn't have done the game, but I missed the closed date deadline and didn't want to come off it.
I'm inclined to think that if you're good enough, you'll get there eventually, but it may take two identically good referees a very different amount of time due to a little bit of luck for one where the other misses out. I think this assessment day idea is a great initiative which will even out that luck element as much as possible, as there is no perfect system which doesn't leave a little bit to luck.