It sounds like a more realistic motivation for that would be to reduce the risk of failure- if the primary team flubbed the project, the secondary team would still be an option. (Such a system would also give you an opportunity to judge how effective either team was.)
Awful thing to do to engineers, but you can understand why management would do it and why they wouldn't want to demoralize the secondary team by telling them.
Awful thing to do to engineers, but you can understand why management would do it and why they wouldn't want to demoralize the secondary team by telling them.