It isn't a myth, Volty.

'Here you are' and 'There you are' are both used like 'voilà!' when we want to draw someone's attention to something. We can certainly use them when we are handing something to a person.

You're welcome, M ******. Still trying to get used to it. :)

Thank you, SuKi. La Liseuse)))

I will never get used to it☹

I tend to use 'here you go' when giving something to someone.

I tend to use 'there you go' when doing something for someone like, for example, holding a door open.

@Volt Age

Generally, I use "here you are" when giving something to someone that they person had asked for.

Person A: Can I have a cup of tea?

Person B: Sure

(makes tea)

Here you are! (passing the tea)

Here you go would also sound natural here. It's not a strict set of rules for using them. It more what sounds most natural. Of course I'm referring to English English, not American English here so I am not sure if there are any differences between the two countries regarding this.