Someone asked this question 3 years ago and never got an answer. I have the same problem: I change the parameter values for my wild cards, delete many already generated data points. Then I try to regenerate with the new set of parameters, but in fact my new data points are exactly those previously generated and deleted.
I have checked, for example, generating 20 points, deleting 10, changing parameters, then generating another 20. Of the new 20, the first 10 are exactly those I had previously deleted. I tried doing this with all three possible options for how to add a new item (keep previous, regenerate only non-shared, or regenerate all wild cards). My wild card data set is set to shared and synchronized. My moodle version seems to be 3.8 (must verify). Thank you!