TimK560: So it seems to be totally random. I don't put much if any stock in the quide above.
While that's fine you believe it to be totally random and don't put any stock in the guide, the fact remains the guide has been verified by many players over the years, and it is not random.
For those who take the ranked-rounds approach to tiering up, the guide is accurate. Over the years, without fail, every single person I've ever seen state the guide is not accurate has either (a) misinterpreted the guide in some significant way, or (b) simply miscounted their ranked rounds.
So, are you certain all 770 rounds you played at TL actually count toward saturation? Is it possible you are including some rounds in that number that don't count? Examples of rounds people usually include in their ranked rounds that don't count toward saturation are the following: Par 3s, Par 5s, or Custom Courses.
The biggest mistake I see players make in counting rounds is they simply note how many rounds they had when they tiered up and use that as a base for counting number of rounds at their current tier.
For example, maybe they had 500 rounds when they tiered up to Tour Legend. So, they figure when the number in their stats gets to 1,250, they played the required 750. And they might have played the required 750, provided they played no Par 3s, Par 5s, or custom courses.
Anytime one plays a ranked round, it's included in the stats. That does not necessarily mean it's included in the saturation number for that tier.