using (TransactionScope scope = new TransactionScope())
using (DbConnection connection = GetOleDbFactory().CreateConnection())
connection.ConnectionString = connStrGoodOleDB;
As you can see the above code only opened a connection, but in SQL Server profile trace, it showed I have DTCTransaction for SQLOLEDBAPP
Then I collected process monitor, and checked the stack of the whole process, found it was due to the System.Data.Oledb.OledbConnections, in the Open() function, it will check several condition, if meet, then it will automatically Enlist the transaction, and finally went to the DTC transactions related call.
And one of the conditions check was OLEDB Services, so I searched for it and found we already had a document noted this issue: