When using the button on mobile, keep in mind that its height might change based on the preferred font size that the user has set system-wide for accessibility purposes.
When using a screen reader, the title of the button will be read out loud, which is another reason to make the title contextual, so people completely relying on the screen reader will also understand what the action is tied to.
It's also important to keep button copy short. Longer copy is harder to scan, and adds to users’ cognitive load. Text might also double in length when it's translated.
To make sure the user always knows what’s going to happen when they click or tap a button, the text must always be fully visible with all of the accessible font sizes and languages we support. That’s why we never truncate button text. Instead, the text wraps and the area of the button grows based on its content and accessible font size.
So on small devices, the button could take up way too much of the screen if we use more than a few words. This decreases the usability of the other parts of the screen, especially if the button is pinned to the bottom.