I was curious. I searched for the NCV3 2008 power steering information. I didn't bother with VS30.
ATF+4 is included in the 2008 Operator Manual as acceptable power steering fluid.
My personal opinion is that for power steering light hydraulic fluid either ATF+4 or ATFIII aka MB236.10 or .12 or .14 spec fluid is fine. It's not like the difference between ATF+4 and ATFIII properties is critical for a simple power steering fluid system.
As an aside.
The VS30 Sprinter 2.0L M274 L4 turbo
gasoline engine specifies only MB229.5 spec oil as being officially approved.
From the above information.
Back in 2008 Mercedes approved MB229.31, MB229.3, MB229.51, MB229.5 spec engine oil for the M272 gasoline engine offered in Sprinters. Mercedes must have some reason for no longer recommending the newer formulation MB229.31 and MB229.51 spec oils for engines which don't have a DPF. Maybe the simple answer is that the original MB229.5 additives are still good for an engine, but just not good for a DPF. If your engine doesn't have a DPF then it doesn't benefit from the newer formulations.
But back to the Power Steering topic.
vic