The main reason for round 16 was that, being 2 separate groups, there's a number of pairings that would never happen (for example a Gisele (Group A) vs Lorena (Group B)), so this round was to give the possibility of some of these matches to happen.
Then again, by that logic we could have had multiple extra rounds A vs B, so having just one might be indeed kinda arbitrary. But having more would have also made too long of a regular season.
But also it was so that each of the 16 models had 16 matches on that stage of the competition.
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Glad you all enjoyed it!
I'll start posting the results later today
That's the spirit!