My humble observation, EK maintains a rather comprehensive profile database on all passengers. This information extends well beyond notes by staff (call centre/ office/any point of interaction with the passenger).
They could create generic profiles about passengers from fares purchased, purchase and payment methods, loyalty, seat and meal selection, bags travelled with, you name it.
How they use this information is what I know little of. The only thing I have had glimpse of was data fed (not from EK) to a rather smart software used by law enforcement and intelligence agencies.
If you decide to fly dark, that is book through a large ota, have no ff number or seat preferences, they could theoretically link this new passenger ID to profiles that match not just the obvious name, dob and phone numbers, but more importantly, individuals of interest that you flew with or have joined you at a destination. And this was 7 years ago.
The analysis was then done in post, but they could very well be doing this in realtime.