AIR TAG tracking questions

What exactly lets you know if a loved one has placed an AirTag in your belongings with the purpose of tracking you?

what are the parameters that registers an AirTag as “moving with you”?

I recently received this notification after spending the day running errands with my spouse. We later went to a friends for dinner, which is when I received the notification.

This AirTag belonged to my spouse, and it had supposedly been in his bag the whole day. But he also had his phone with him, which would be linked to this air tag, so presumably, a “moving with you” notification would’ve be necessary since it was with its rightful owner and not being used to track me.

I also had my own phone with me linked to my own AirTag in my purse, but my partner did not receive this “moving with you” notification.

This has made me ask the question, why would a person get this possible tracking notification when travelling with a partner? If said AirTag is with its assigned cellular device, and not displaced from its owner, why would this notification come in at all?

How close does an AirTag need to be with you, and for how long, before getting this notification? Does it need to be closer to one’s own cellular device, for example (such as if my partner had actually put his AirTag in my purse) than it is to its owners cellular device? Would it have had to of travelled with me without him for a period of time in order for this to happen?

I don’t need the “if you’re suspicious your partner would track you you should reconsider your choice in spouse” type of comments. There’s plenty of cases in the world where the person you’re involved with romantically turns out to be someone different than you’d thought, and plenty of examples with AirTags in particular where unsuspecting people have been tracked by loved ones when they never would’ve ever expected someone they loved to be capable of such a thing … and when you have a history of having an ex who stalked you, having something like this happen with a new partner can be quite unnerving. So I just need to know the logistics / facts of how these devices work in terms of knowing without a shadow of a doubt that my partner did not plant this device on me.