From a comment in a github issue regarding this:
IMO, this is not right. Armed ships should be able to set ambushes. Armed ships should be able to stay aggressive while hidden.Geoffthemedio wrote:it's quite plausible that if a fleet is agressive/controlling its system, then it should have to reveal itself to do so, and thus be visible already on the first round of combat. This doesn't prevent such ships from being used, but they would need to be in passive / hidden mode to be hidden on the first round of combat.
The workaround of having a non-hidden ship set to aggressive along with your passive hidden fleet, in order to trigger the combat with your armed fleet hidden during first round of combat, is awkward and annoying in the same way than having to constantly replace the comsats to trigger your planetary defences attacking passing enemies. IMO, this makes hidden armed fleets way less interesting.
If this change was fixing some problem, it would be great to know what problem was that and see if that can be fixed in a better way that does not make annoying to play stealth fleets.