Not intentional? There is no way nobody at f2pool didn’t notice that they don’t mine blocks with shielded transactions for 2 years. These guys obviously have top notch programers in their field which pretty much excludes the “not intentional” theory.
Doesn’t even matter too much. It’s enough that there is a problem that can get bigger and there seems to be several incentives even to do so as f2pool does, as stated in the article. The problem sounds way bigger than just a “not intentional, everything is fine” …