https://code.visualstudio.com/docs/cpp/config-linux

From now on, the play button will read from tasks.json to figure out how to build and run your program. You can define multiple build tasks in tasks.json, and whichever task is marked as the default will be used by the play button.

Is the bold incorrect?

Isn't the play button is about launch configurations i.e. launch.json. The current launch configuration contains a preLaunchTask for which task it will run.

Next, you'll create a tasks.json file to tell VS Code how to build (compile) the program. This task will invoke the g++ compiler to create an executable file from the source code.

This line can probably be removed altogether. It mentions tasks.json which has already been described earlier on that page.