Great outcome!

I doubt we will ever know what the criteria for discretionary renewals are except in the most general sense - like the upgrade algorithm, it is in their interests to keep the details firmly under wraps. About the only thing we can say with any certainty is that they are not doing it out of any sense of altruism or rewarding loyalty! Rather, someone, somewhere has bet that keeping you on the status treadmill will ultimately bring in more money. And they may well be right!

[And I mean no criticism by the above, this is the sort of tactic that would undoubtedly work on myself for example!]