If you have recommender enabled for a size chart, by default, the app will also inject a "what's my size" link, which will open the recommender tab directly. The link also changes content depending on when a recommendation is made. As you can see in the following screenshot, there are three states of the button.
If you wish to remove this, go to settings and click on the "Recommender" tab.
Then, in the sizing injection selector, you can select the injection as "Do not inject".