How does the game determine whether you are "caught off guard" in Legends: Z-A?

Question

In the Z-A Royale, if you are spotted by a trainer, sometimes you get stunned with the message "You and your Pokemon were caught off guard!"

In theory it should be for when a trainer sees you without you seeing them, but in practice it seems wildly inconsistent. Sometimes I'll be attacking them and still get that message if they notice me at the last second, and sometimes trainers that I genuinely missed don't give that message. I've even gotten spotted despite visibly knocking out the trainer's lead Pokemon and causing them to send out their second one.

I am interested in how exactly the game checks for getting "caught off guard" from a technical perspective since the inconsistency is kind of amazing to me.

Comments

I’ve ran up to try and talk to a trainer and I’ve gotten caught off guard. When I was looking at them. Right there. Pokemon out.

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I was just about to ask this; I've been caught off guard staring at them as they turn around at least five times in the past 30-odd battles. Does crouching have anything to do with it?

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It's when the npc (trainer) spots you while you're attacking them. For exemple, my aegislash is changing forms to attack, and the npc turns around and sees me. Then the game recognizes it as you being "caught off guard".

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I am not convinced this is a comprehensive answer, as there’s been times I’ve been caught off guard and have not been attacking.

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I'm looking for an answer on how the game determines it in the code, as in what parameters are used; I suspect that it may have something to do with relative angles... regardless, it's easily seen through normal play that you can be seen attacking without getting the message and that you can get the message without attacking. The inconsistency is why I'm wondering how it's programmed, knowing how it works can help optimize time-saving strategies