You know how the scientific definition of theory has a fundamentally different meaning as the colloquial meaning of theory? The anarchist definition of property is synonymous with capital while the colloquial idea of property is more synonymous with the anarchist definition of possessions.

I am physically able enough and have the ability do almost all the necessary maintenance on my house, car, and other possessions myself. Of course everyone needs expert help from time to time, for example I can solder copper pipe but I don't want to risk a gas leak so I call a HVAC tech if I need a new furnace valve. However other than external inputs like water, power, gas, and internet service which intrinsically require collective effort, a single person (who is physically able enough) can efficiently maintain a modern house by themselves.

A single person has no way of doing anything but very basic maintenance on something as technologically complex as a modern factory. Even if they were a master mechanic, electrician, calibration engineer, and every other diverse skill set involved in just maintaining a factory it would be impossible for them to run it as anything but an inefficient workshop without some sort of external labor. Things that intrinsically require collective effort to function should be collectively operated for the benefit of the community.

The same is true for a large property like a mansion (which should not really exist beyond serving a purpose as a historical artifact), an industrial farm, a power generation facility, or a water treatment plant. If it requires collective effort to run and maintain to function it is capital, thus falls under "property" and should be collectivized.

The fact that someone can own and profit off something while unable to maintain it or use it without collective effort solely for their own benefit and enrichment is theft. Without their workers they would have a decrepit building full of the rusting hulks of machinery yet there are factory workers in the US who have to sleep in their cars or work multiple jobs while the C-Suit takes home millions.