Reading that, I suspect the title should be “A quantum experiment suggests there’s no such thing as observed objective reality”
The experiment shows one can do a measurement of polarisation and the “friend” sees if a measurement has been done yet (still in superposition). This is an observation problem. They do not mention if the polarisation is the same when measured by the friend. Is it just splitting hairs on terminology and shows a problem in the socalled “collapse of the wave equation” when observed that needs to be solved, rather then the reality of the polarisation of the proton?