Another oil question
 

Here goes...
Since Porsche's approved oils are ACEA A3/B4 oils, would it be safe to expect that any oil with the ACEA A3/B4 designation is safe to use?

Probably, as long as it was the right viscosity also.

But why bother? There are so many good A40 oils out there, in every price range, that you may as well just use an approved oil.

One of the sensitivities of the M96 to the geekish details of oil spec is "foaming" aka aeration . Suggest you search that issue. Then compare film strength/thermal stability/shear strength. It has been well covered here and elsewhere. But faith more than tribology seems to influence lubricant choice.
There are better choices now than the Porsche recommended Mobil 1. A useful benchmark often recommended is Joe Gibbs DT40 (search JGDT40).