They overloaded the button to load Siri if its held for even a fraction of a second too long. 99 times out of 100 I don't want to use siri but she continually pops up.
Trying to click to get back to the home screen.... here's Siri.
Trying to double click the button, to kill an app..... here comes Siri
So to answer the question....
1) They made Siri enabled by default, something that I can't see myself ever wanting.
2) They made Siri come up using the button, again something that almost always means when siri comes up its by accident and not indented.
Apple isn't immune from "dark patterns" in their UI. The Siri example above being the most egregious example I can think of.