I don't see why a Wave Serpent wouldn't be in the formation. A Dedicated Transport bought for a CAD is in that detachment, so a Dedicated Transport bought for a Formation is in that formation.
The principle is correct, but the terminology is not. Wave Serpents are not part of a unit - they are a seperate unit that is also in the Formation (and shares a slot in a Force Organisation Chart). No real difference for this argument, but just a heads up for future discussions.
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