maneater been there, done that question

When do have to reveail what options you have chosen; is it when the unit is deployed or when it uses an option e.g. swiftstride?

Straight from the FAQ

Q: When do you reveal what special rules a unit of Maneaters has
picked for their Been There, Done That special rule?
A: When you deploy them

thanks

Is there any rational for why you have to reveal that otherwise juicy information?
Is it because it is a special rule rather than an upgrade option?

[Opponent] "Hey..."

[You] "Yeah?"

[Opponent] "Why are your Maneaters deploying as though they had Scout?"

[You] "Uhhmm... No reason..."

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It would probably be a bit hard to hide some of the options for Been There Done That, and it seems unfair asking the opponent to guess which of the other rules is being used