I think none of us is "wrong"...Interestingly, like Kaeru I have known this type of game for more than 30 years & I was taught that diagonal was an allowable move. Maybe I have had it wrong all these years....
it's just that you are living at the other end of the world (or we are, from your point of view) so surely rules can differ.
perhaps include a switch to allow/disallow diagonal moves....?