Well, the opening paragraph of the article does say:-
"that the company secretly slowed certain iPhone models to preserve battery life"
and I haven't seen anything about encouraging people to upgrade their phones, if anything, it appears to be discouraging that as the phone will last longer. The article then says:-
"offered a discounted battery replacement program"
which, again, seems to be the opposite of the idea of making people upgrade.
If anything, Apple should have been more open about it from the start that the throttling was being used to extend device life - but that's a UI issue more than anything (and good UI is hard!).
Have I missed a bit in the article?