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.
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.