[semiquaver]

Every real world use of Web Components that I’ve seen uses <template> elements and/or imperative DOM methods to implement rerendering. These are blazing fast and exactly what React uses. It’s possible to build a slow app using Web Components, but that’s true of every library, including React.

[Izkata]

Same here; I suspect they've mixed up defining the component (where some examples do use innerHTML) and using the component (which don't).