The oils are all miscible, for sure.
But that doesn't guarantee any sort of performance level...two mixed SN oils, particularly different manufacturers cannot be stated to pass any of the test requirements of SN (other than the miscibility standard obviously).
There's a difference between "nothing blew up", and SN level performance. If the OP understands that, there's nothing "wrong" with it, but if he's expecting the brew to start at Lebanon Kansas mid winter, he's best not doing it.
The oil manufacturers all state that mixing is acceptable, but not recommended...but that nothing seriously 'bad' is likely to happen.