Output SqlParameter value not populated when using SqlCommand ExecuteReaderAsync with using declaration - using

Question

I am running this stored procedure:
CREATE OR ALTER PROCEDURE dbo.usp_test
#Result int OUTPUT
AS
BEGIN
SELECT Id FROM Table1;
SET #Result = 101;
END
GO
In my code, I notice different behaviour depending on how wether I use a using statement, or a using declaration.
using statement (C# Reference)
With a using statement
await using var connection = new SqlConnection("...connectionstring");
await connection.OpenAsync();
await using var command = new SqlCommand("usp_test", connection) {CommandType = CommandType.StoredProcedure};
var outParam = new SqlParameter("Result", SqlDbType.Int) {Direction = ParameterDirection.Output};
command.Parameters.Add(outParam);
var items = new List<int>();
// using statement
await using (var reader = await command.ExecuteReaderAsync())
{
while (await reader.ReadAsync())
{
var id = Convert.ToInt32(reader["Id"]);
items.Add(item);
}
}
var availableItems = Convert.ToInt32(outParam.Value);
In this case I get both the list of Id's in items, and the expected value of 101 in the output parameter result.
With a using declaration
await using var connection = new SqlConnection("...connectionstring");
await connection.OpenAsync();
await using var command = new SqlCommand("usp_test", connection) {CommandType = CommandType.StoredProcedure};
var outParam = new SqlParameter("Result", SqlDbType.Int) {Direction = ParameterDirection.Output};
command.Parameters.Add(outParam);
var items = new List<int>();
// using declaration
await using var reader = await command.ExecuteReaderAsync();
while (await reader.ReadAsync())
{
var id = Convert.ToInt32(reader["Id"]);
items.Add(item);
}
var result = Convert.ToInt32(outParam.Value);
In the example above, I get the list of Id's in items, but the result is 0.
What is going on here?
I'll be adopting the pattern that works, but I worry that some well-intentioned future developer will see the using statement and replace it with a using declaration because it looks nicer and be unaware that he's breaking something.