it really works that way yeah, I spent 7 days in total darkness without any sensory input and I came out with a totally rewired brain too sensitive to the digital barrage of information and inputs, so it had to adjust again back to more erratic mode over some time
There are people who provide it as a service in their countryside house or specifically developed cabins for this. It is usually referred to as "dark retreat" so try to Google if there are any around your area. I did it in Czechia, where it's pretty popular.