no it says you can duplicate data slates. war engine "choice" under the blood pact detachment is just a dataslate not a formation.

An army may not have a duplicate of any Detachment.
Note: This includes “Decurion Style” Detachments which are comprised of multiple data slates and Formations. They may not take duplicate Formations within the Detachment, although they make take duplicate Data Slate units within the Detachment if permitted to do so.
- See more at: https://www.frontlinegaming.org/comm....6iBU33FG.dpuf