Edit: Ok to be fair, there was this post:
https://hive.blog/hbd/@smooth/why-i-set-my-witness-hbd-interest-rate-parameter-to-3
So was there enough discussion? Maybe not, but changing the APR is just a witness parameter, it didn't require coding, and could be changed back to 0 (or any other value) easily.
It didn't happen. There was a relatively brief discussion on the semi-private mattermost witness channel, Smooth brought up the idea, changed his witness and many others adapted quickly.