It's different when it's oil draining back from the heads as opposed to a turbo oil return as is being discussed here:

a) The turbo oil return is coming directly from high speed bearings, so the fresh oil supply cannot be hindered

b) There is a much bigger pressure head on the oil coming from the heads on that engine. The oil leaving the turbo is doing so from no more than about 100-150mm or so above the oil level in the sump, hence all the talk of pressure differentials.