Your code looks correct; here are my suggestions.

1. My best guess is that something you may have specified in the Nlog config is overriding the configurations in appsettings.json.

To test this, could you add the following inside services.AddLogging()? Since this filter is at the code level, It should help override NLog settings.

logging.AddFilter("Microsoft.EntityFrameworkCore.Database.Command", LogLevel.Warning);

2. Do you have an Nlog.config file, and if so, confirm if a more permissive rule is specified for Microsoft.EntityFrameworkCore.Database.Command?