From Guilherme Rambo (you might know him as one of the folks digging through the leaked HomePod update):
What if the lock button becomes the home button? ?
— Guilherme Rambo (@_inside) September 2, 2017
The concept of the iPhone lock button as the new home button has been floated around for quite some time. But Guilherme is not just guessing here. He is reacting to this particular string he encountered:
There is an implementation in SpringBoard to invoke Siri by long pressing the lock button ? pic.twitter.com/f2uB3JGZxW
— Guilherme Rambo (@_inside) August 31, 2017
In a nutshell, that code at the top of that second tweet refers to a gesture to launch Siri from the lock button. Interesting.