I followed the steps to recreate your problem, I could find a work
around.
Add a ListChanged event for the detail grid binding source
(orders_FK00BindingSource) and add the code to modify the TableStyle,
I have added the example below.

You need to add the other columns with the width of your choice and
remove the replicated code from the InitializeComponent()
If you run the code you will only see 3 columns and the width of
OrderID column is 10.

Hope this helps,
Cheers,
Arun

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private void orders_FK00BindingSource_ListChanged(object sender,
ListChangedEventArgs e)
       {
           System.Windows.Forms.DataGridTextBoxColumn
order_IDDataGridColumnStyleDataGridTextBoxColumn;
           System.Windows.Forms.DataGridTextBoxColumn
customer_IDDataGridColumnStyleDataGridTextBoxColumn1;
           System.Windows.Forms.DataGridTextBoxColumn
employee_IDDataGridColumnStyleDataGridTextBoxColumn;
           order_IDDataGridColumnStyleDataGridTextBoxColumn = new
System.Windows.Forms.DataGridTextBoxColumn();
           customer_IDDataGridColumnStyleDataGridTextBoxColumn1 = new
System.Windows.Forms.DataGridTextBoxColumn();
           employee_IDDataGridColumnStyleDataGridTextBoxColumn = new
System.Windows.Forms.DataGridTextBoxColumn();
           //
           // order_IDDataGridColumnStyleDataGridTextBoxColumn
           //
           order_IDDataGridColumnStyleDataGridTextBoxColumn.Format =
"";

order_IDDataGridColumnStyleDataGridTextBoxColumn.FormatInfo = null;

order_IDDataGridColumnStyleDataGridTextBoxColumn.HeaderText = "Order
ID";

order_IDDataGridColumnStyleDataGridTextBoxColumn.MappingName = "Order
ID";

order_IDDataGridColumnStyleDataGridTextBoxColumn.PropertyDescriptor =
null;
           order_IDDataGridColumnStyleDataGridTextBoxColumn.Width =
10;
           //
           // customer_IDDataGridColumnStyleDataGridTextBoxColumn1
           //

customer_IDDataGridColumnStyleDataGridTextBoxColumn1.Format = "";

customer_IDDataGridColumnStyleDataGridTextBoxColumn1.FormatInfo =
null;

customer_IDDataGridColumnStyleDataGridTextBoxColumn1.HeaderText =
"Customer ID";

customer_IDDataGridColumnStyleDataGridTextBoxColumn1.MappingName =
"Customer ID";

customer_IDDataGridColumnStyleDataGridTextBoxColumn1.PropertyDescriptor
= null;
           //
           // employee_IDDataGridColumnStyleDataGridTextBoxColumn
           //
           employee_IDDataGridColumnStyleDataGridTextBoxColumn.Format
= "";

employee_IDDataGridColumnStyleDataGridTextBoxColumn.FormatInfo = null;

employee_IDDataGridColumnStyleDataGridTextBoxColumn.HeaderText =
"Employee ID";

employee_IDDataGridColumnStyleDataGridTextBoxColumn.MappingName =
"Employee ID";

employee_IDDataGridColumnStyleDataGridTextBoxColumn.PropertyDescriptor
= null;
           //
           // ordersTableStyleDataGridTableStyle
           //
           this.ordersTableStyleDataGridTableStyle = new
System.Windows.Forms.DataGridTableStyle();

this.ordersTableStyleDataGridTableStyle.GridColumnStyles.Add(order_IDDataGridColumnStyleDataGridTextBoxColumn);

this.ordersTableStyleDataGridTableStyle.GridColumnStyles.Add(customer_IDDataGridColumnStyleDataGridTextBoxColumn1);

this.ordersTableStyleDataGridTableStyle.GridColumnStyles.Add(employee_IDDataGridColumnStyleDataGridTextBoxColumn);
           this.ordersTableStyleDataGridTableStyle.MappingName =
"Orders";
           //
           // ordersDataGrid
           //
           this.ordersDataGrid.DataSource =
this.orders_FK00BindingSource;
           this.ordersDataGrid.TableStyles.Clear();

this.ordersDataGrid.TableStyles.Add(this.ordersTableStyleDataGridTableStyle);
       }