Why the sqlclient telemetry uses db.system instead of db.system.name?

[jundayin]

Based on the convention spec, I only see db.system.name, but the instrumentation library is returning db.system

[Kielek]

You are referring to the registry. In this part it is true.
For now, instrumentations relays on semantic convention 1.24.0 which required db.system.
There is an ongoing effort to migrate to the latest version, the goal is to have it in place when the database semantic convention reach stability.
For now, 1.30.0 is marked as release candidate.

You can check the progress in the CHANGELOG for SqlClient. You might be interested in OTEL_SEMCONV_STABILITY_OPT_IN env. var.