[mdc-top-app-bar] component claims to have a fixed variant but the default is fixed and can't be changed.

[rockyjvec]

Having "Fixed" under the "Other Variants" section of the documentation makes it seem like being fixed is optional.

The base, mandatory class of the component always adds the style "position: fixed", so it's not possible to have a top app bar that isn't fixed without custom css that overrides the base class: https://github.com/material-components/material-components-web/blob/2a6ddc1cff903da5e17766a214d76fc8cb3904d8/packages/mdc-top-app-bar/mdc-top-app-bar.scss#L39

Shouldn't the "position: fixed" style get added in the "mdc-top-app-bar--fixed" class instead of the base, mandatory class?