Hello. This decoupling between the Data Adapter and the activity of the single clients is intentional.
The Data Adapter only manages items, whose fields only depend on the item characteristics.
In this way, multiple client subscriptions can share the same server-side "subscribe" invocation to the Data Adapter.

The client activity is available on the Metadata Adapter (see notifyNewTables).
If you want to modulate the Data Adapter activity based on the current client activities you should have the two adapters communicate at application level.
Alternatively, you should do without subscription sharing and define different items (by using different item names) when the involved field set is different.