No one knows exactly how or why Disney exercises ROFR, we all just have guesses.
I beleive that Disney can repackage a large contract into a number of smaller ones, UY has to stay the same though, so it doesn't really matter what they take.
My personal thought is that ROFR is driven purely by how many people are waiting for points on the wait lists. Given that they can wait 30 days for every contract, that givens them a 30 day window to wait to see if anything better comes in during that time.
If you look at the data from the last 12 months, the average size of a contract that was ROFR was 211 points. I've seen 50 point contracts taken and I've lost a 400 point contract myself. It's probably nothing more than what the average contract size is out there, so I don't think that there is any relationship between contract size and chance of getting ROFR.
Your best chance of passing ROFR is having someone else submit the same resort and UY year with a lower price at the same time as you