The process I went through was basically thinking about my core habits, mapping said habits to some objects, and then thinking about extra objects to support those habits. After that, I slowly started purchasing what I needed. Timing was great, because I sync'd that with moving countries. I spent some effort thinking about quality of individual purchases, and I ended up with a very minimal home, which is also great for maintenance.
For a different lifestyle, this list would be much longer and that is fine.
There is nothing special about having just 100 items.
Depending on where you are located geographically there may very well be something special.
I live in the PNW and I bet if I counted all my forks, spoons, coffee cups, pots and pans, etc., I'd have more than 100 items right there, to say nothing about my tool chest. Between my home office and my wife's purse I probably have 100 pens and pencils around the house.
To own a grand total of 100 items would be extremely spartan for just about anyone around here.
But if you are renting a condo downtown, as it was my case, you may want to trim down your possessions as much as possible.
Nonetheless, I think people tend to own too much stuff and this prevents focusing on what actually matters, it's a bit like with bloated software.
On this I agree with you wholeheartedly. It's very easy to accumulate cruft that one "might need later". I have a whole toolbox full of that shit. I might actually need a bunch of random capacitors, who knows?
There is no way that an adult has 100 things inside an entire flat they eat, work, leisure, and sleep in. I assume that they mean 100 valuable things that they wouldn't want to just lose.
Of course, the shower isn't yours so it doesn't count. Using this, we can get rid of the sleeping bag and just roll up the carpet in the rented flat and sleep in that.
What else can we cut?
Once a year walk through every room in your house with a video camera, openning all drawers and closets and record it all. Drop your 20-plus gigs of high-dev video somewhere (I use AWS glacier for pennies a month) and then IF you ever need to, you can painfully go through it and catalog everything.