Apple watch not mirroring iPhone texts messages

I just found out from Apple tech support that mirroring text messages just means that the SMS and iMessage texts go to both devices, your Apple watch and your iPhone. However, if you delete the message on one, or read it, it does not reflect it on your other devices being 'mirrored'. The way it was explained to me is the Apple watch text messages are kept on a different location than the iPhone texts, so, an update to one is not an update to the other. Supposedly you have to delete them on both devices if you want to delete a text.