I believe the point they’re trying to make is that they have access to APIs which describe particular software on your PC. You can argue based on the fact that, yes, the software is persisted on your filesystem. However, the API they access brokers [meta]data about the software. It’s not a filesystem API. If I add arbitrary files to an extension directory under my browsers path for extension persistence, they probably cannot see those arbitrary files unless the extension is built to allow it.

There is a big difference between having direct and broad read access to the filesystem, versus the much smaller volume of data they can infer about your filesystem using APIs for browser extension data.