The update introduces a new feature which allows you to quickly perform Reactions in-game by using your smartphone. As you can see in the image below, you can simply tap on your chosen Reaction from a menu, getting rid of the need to cycle through your favourite poses on your Switch.
The update doesn't appear to have rolled out everywhere at the time of writing, so don't worry if you can't find the option to use Reactions on your NookLink app just yet. We're sure it'll be with you very soon indeed.
In the meantime, let us know what you think of this new feature in the comments. It sounds like it'll make communicating with friends much easier when checking out each others' islands!