Siri data stored for up to 2 years

Apologies if this has been covered, i haven't spotted it anywhere else and i'd like to share a little something i saw earlier today.

The article alleges that Siri retains your requests for six months and then they're stripped of identifiers and stored elsewhere for up to a further year and a half. I found it a little strange because in my limited use with Siri it doesn't seem to call on previous queries to make predictions or help with results like Google Now so i was surprised to hear this. I guess we all accept that some amount of data will inevitably be shared these days but i hadn't heard of this before.