P2WSH-MultiSig fails with documented OP_0 workaround
The real requirement is that the extra input to OP_CHECKMULTISIG is a zero (that is: the empty byte array).

For non-SegWit inputs, the only canonical way to get such a zero on the stack is by including an OP_0 in the scriptSig. OP_0 just pushes an empty byte array onto the stack.

In SegWit inputs there is no longer a script to build that stack. Instead, you specify the stack directly. As a result, not just the recommended way, but the only way is adding an empty array to the scriptWitness.