Hey, I ran into a similar issue recently - I found by using Microsoft.Data.SqlClient instead I got the full command text.

There is a note in the README that implies that command text is not available using System.Data.SqlClient

When using the built-in System.Data.SqlClient only stored procedure command names will ever be captured. When using the Microsoft.Data.SqlClient NuGet package (v1.1+) stored procedure command names, full query text, and other command text will be captured.

(Last note under this section https://github.com/open-telemetry/opentelemetry-dotnet-contrib/blob/main/src/OpenTelemetry.Instrumentation.SqlClient/README.md)