I agree with this one and noticed the problem with the first guest I was trying this feature. I have created my messages in 4 languages and they were all sent which was not very convenient. So due to this I stopped using the feature completely as it took me more time in selecting the messages I wanted to include, than just select it manually each time I need to send a message to the guest.
Also another thing that would be useful is being able to filter the message templates somehow as my list is quite long due to the fact that ALL my messages are in 4 languages and for each property its usually different so it takes a long time too scroll and find the message you are looking for. @Airbnb