Helllo,
The maximum load of 4 concurrent query requests limit for Windows libraries mentioned in the Microsoft documentation refers to the number of concurrent operations (for example, searching, indexing, or retrieving metadata) that can be processed at the same time against the library. If more than 4 queries are attempted at the same time, performance may degrade or some queries may fail. This is not directly related to the number of connected users or devices.
Best Regards
Zunhui