I have seen all kinds of different flames used. The idea of the oxydizing flame being bad is that it has a lot of oxygen in it, and this will tend to supply oxygen to the hot metal increasing the chance of oxydizing the steel. This is a reality with gas welding on steel, since no flux is required. If your flux is holding up then your steel is protected from oxydation so this ought not to be a problem. So it could be yet another crossed line with welding lore.