[b42]

> To opt-out from our anonymization of your personal information to perform data analyses, please provide your Mastercard or Maestro payment card number below.

This sounds like they are going to continue using my purchase data but without anonymization? Not a native speaker so perhaps I'm just misunderstanding the sentence.

[l33tman]

I think they tried to formulate it so it will sound less damning for them, like they want to make it explicit that what they performed their data analysis on is your anonymized personal information.

[52-6F-62]

You're right. I don't think that's the intention, but that is certainly what the language implies. It's rather vaguely worded.