Now sure they could say every individual think they do with this data. But, Apple makes it clear they collect and use this information to improve Siri. What else do people think this means?
That you link an investigative Wired article shows that most people aren't going to know this information. Siri users aren't all 2013 Wired readers, nor are they waiting around to hear what an Apple spokesperson is going to clarify.
Frankly, Apple should at least prompt people even just to be the good guy when it comes to privacy fallout on all these services.
Granted, that might not seem like enough, but it was clear enough IMO.
It would drive the point home if Siri just said, every N queries, "anything you say to me can and will be sent to Apple's servers for analysis purposes".
As to regular pop ups or messages, that’s simply a worse user experience for zero benefit.
There is a reason I don't have an echo/home/$other. There is a reason I don't use cloud stuff for my personal life(where practical) I don't have web enabled CCTV, I don't smart locks, I generally don't have stuff with cameras in them.
There is evidence for suggesting that the anonymisation apple uses is quite good. Unlike with alexa, siri recording I don't think have been used in court cases. This means that apple are fairly sure that they can't recover people's recording, on pain of contempt of court.
Why is that important? because it means that its most likely GDPR compliant. If you are an EU citizen, I fully recommend you doing a subject access request, to see what data they hold on you. You are within your rights to have that data deleted, or amended. Or if you so wish, none of your details to be ever processed again.
Now, sadly for the USA, your protections are frankly shite. I suspect you'll have to lobby your local politicians.
Just because you want to improve your product, that doesn't mean you can do anything you want. No one should have to assume that the products they're buying are Trojan horses that are secretly spying on them.