The clearing of the ‘whining’ was probably the frequency increasing to being outside of the audible range as the rotor speed increased.
Putting the old oil back!!!!!! Oil screen takes out the lumps and the oil filter removes particles down to ? microns on a single pass before lubricating. No oil filter removes all contamination.
I suspect that both turbochargers failed for the same reason, that reason is unlikely to be the turbocharger.
Don’t go back to the same mechanic for the repair.
