Dedicated transports, i.e. waveserpents, definitely count as being in the same detachment as the aspect host. However it's up for debate as to whether they count as part of the formation as well.
As an honest question, can you quote the source of those rules? I'm not familiar with them. To the best of my knowledge, dedicated transports don't take up a FOC slot, but gain the Battlefield role of the unit they're chosen with. I'm not aware of any rules stating that they necessarily become part of the detachment / formation, though.
It does make me wonder how a person could build a battleforged list that included dedicated transports, unless that was accurate.
On the basis that a unit taking a Dedicated Transport does NOT make the dedicated transport part of the unit, I'd have to say that the transports should not gain benefit from the bonuses. Since the rules tend to be restrictive [only rules that fit in the box] instead of inclusive [so long as part of the rules fit in the box] and the rules specify that certain units [that don't include Wave Serpents] are part of the formation, the transports shouldn't benefit.
Unfortunately, that leads me to the question of, "If I take this formation, and purchase WS transports for the units, and the WS aren't part of this formation, does that mean my list is Unbound?" By RAW, I think the answer would be yes, it is unbound, so no benefits for anyone.
Unless you take another detachment, that you could include empty Wave Serpents. Maybe a CAD to farm the FA slots for WS.
Also, since Wave Serpents can't include Exarchs, and that's a requirement of being in the formation, that would also seem to exclude Serps from being part of it.
Rather than asking if Serps can gain benefit from the formation, it would be more piercing question would be whether they can be part of this formation at all. I'm pretty sure the answer is no.