In transaction, @@IDENTITY return other table id, is it a bug?

My project use:
Dapper 1.50.2
Dapper.Contrib 2.0.0
DapperExtensions 1.6.3

and my code like this:

var sql = "insert into tb(name) select 'aaa' from dual where not exists(select 1 from tb where name='aaa')";
using(var connection = factory.CreateConnection())
using(var trans = connection.BeginTransaction())
{
    if(connection.Execute(sql, null, trans) > 0) 
    {
        return Convert.ToInt64(connection.ExecuteScalar("SELECT @@IDENTITY", null, trans));
    }
}
return 0;

while I published the code, I found "SELECT @@IDENTITY" returns other table's autoId, not tb's autoId?
Is my code wrong? how to fix it?

Start by identifying the database provider returned by factory.CreateConnection and reproduce the transaction using the SQL shown in the issue. Check whether the provider's @@IDENTITY behavior accounts for the returned value; done means establishing whether Dapper is involved and documenting a confirmed fix or limitation.