Thanks for this comment and question, Steve.
The short answer is: yes, this elegantly demonstrates Einstein's theory that gravity is a classic fictitious force and earth's surface accelerates outward. It can be argued that Newton would not make a different prediction based on spring physics. But a typical observer such as Newton is convinced the phone on the table is not accelerating upward.
We should think of that analysis as confusion by observers who don't carefully distinguish relativity's absolute or proper acceleration from the phone's coordinate acceleration relative to the tabletop - which is incorrectly presumed to be an inertial frame. Thus Newtonian observers on earth tend to think of the earth's surface as a vertically stationary, and often can't accept that earth's outward surface acceleration is real.
Newtonians likewise have trouble accepting that this is possible because lengths themselves - e.g. the length of a meter - is increasing in the vicinity of matter, as explained in the article. Although stretching of space and time is the core of Einstein's spacetime curvature theory, and the core metric tensor of the field equation spells it out rather directly, it's so counterintuitive that many physicists struggle and deny it.
The accelerometer data just makes the reality substantially clearer and more vivid. Physics professor Brian Cox has more clarity on this than most, and he has many articles and videos that show how indisputable and easy to prove this is, and how different it is from Newton's theory. Here's one:
