There's been pushback for quite a few years. The foundation for which is that we don't know the actual performance of the mixed products, while the individual constituents of said mix have been proven to pass the requirements for the approvals they carry on the bottle. The API requirement for oils to be miscible, as
@Shannow stated years back, is that they don't split like mayonnaise. There's no other performance requirement beyond that, so there's no guarantee that performance will be as good as the individual products as tested, let alone an improvement.