> That explains why what you're saying and focusing on doesn't seem to make sense.

Or it could be just you. Even presuming you're a good programmer, that wouldn't make your arguments good by default.

> Data structures are parts of the program that hold data.

Not according to Wikipedia:

> In computer science, a data structure is a data organization and storage format that is usually chosen for efficient access to data.

ECS doesn't stipulate any storage format, as shown by the previous definitions, only that your application will be architected around Entities, Components and Systems. How they are stored/managed is up to the programs/frameworks/engines to decide, and this storage is just one concern an implementation may have, just like how storing ViewModels is just one concern of a MVVM framework, but not all.

I'm no stranger to using unorthodox definitions, but I would prefer if you were upfront that your definitions are unconventional, rather than pretend that they are common sense without citing any third party authority.