It's not an assumption. Apple has earned a decent reputation for being pro privacy through their actions over decades.
For prior generations, Hoover, Nixon, MLK (how they targeted him), the Church hearings, and many other things provided evidence as to the extralegal behavior of the government at times.
[0] https://www.wired.com/2014/09/feds-yahoo-fine-prism/
[1] https://www.businessinsider.com/the-story-of-joseph-nacchio-...
Apple are better on the privacy front than their competitors, but not by that much.
I don't trust any corporation to actually side against the govt.