You use a "for=[inputID]" in the label element to target the inputs ID not the name.
If you take a look here https://getbootstrap.com/docs/4.1/components/forms/, you'll see that the app was designed to handle form mark-up in the same way as the Bootstrap Dev's have marked-up their forms. I'm sure it's more semantic that way, which is what this app is about. Prototyping Bootstrap sites semantically.