I don't believe for a moment that Trust AI had anything to do with this change, or in fact, the majority, if any of these changes. The AI is more than capable of doing mechanics, unless a specific party member is explicitly programmed to do something stupid (like how Mothercrystal goes, only Y'Shtola is programmed to consistently dodge AoEs), or the player is actively preventing them from doing so. They are really consistent with them.
This change was also done for 8-man trials, that are not supported by the AI.