Sounds like it might have been a targeted promotion, only available to certain members. I do not recall any general bonus being available for reaching 75,000 or 100,000 flown mile levels.
The past 2 years, I have been at 103,000 and 99,000 and have seen nothing like you have described. This year, I should end up at about 80,000 and I plan to defer any other trips until Jan/Feb....for obvious reasons!