Good find! It makes sense to me but I'll check with our designers to confirm that's the intention.

Confirmed this is indeed a bug, though how to best fix it seems questionable.

I'm not sure I agree that a MdRipple.control should be an array, since it maps to the <md-ripple for="single-id"> attribute, and the htmlFor attribute is historically 1:1. It'd be more accurate to say that one control may have multiple ripples.

The ripple itself could try to check and handle a control's labels here to add events, but it wouldn't work for dynamic labels being added or removed to the control:

htmlFor attribute is historically 1:1.

Mm yeah didn't think about that.

Wouldn't it make sense if all components that require a labelEl (i.e. radio, checkbox and switch) would implement the attachableController or rather extend a... lableHavingFormFieldAttchableController-Class since they would probably all do the same.

This could either take in the rippleEl and set the pressed and hoverer state, which have to be made public then.
Or a seperate lableControlledRippleEl and a set control to that.
Not sure which I'd prefer but probably the latter.

Well it's not required that those components have a visual <label>. They can be standalone without a text label.

We could make something like the old <mwc-formfield> that's basically a fancy label, or an <md-label> element, but we lose that support for simple <label>-ability.

Native labels do some interesting things with CSS. They do trigger pseudo class styles. Hovering over this label example will cause the input to show a red outline (jsbin example). This works for form associated custom elements too.

<style>
  input:hover {
    outline: 1px solid red;
  }
</style>
<input id="checkbox" type="checkbox">
<label for="checkbox">Label</label>

Maybe there's a different approach to additionally support the ripple visual when its control matches :hover and :active without pointer events.

Tried this in the internal/_radio.scss and its working rather lovely:

:host(:hover) md-ripple {
  background-color: var(--md-ripple-hover-color);
  opacity: 0.08;
}

:host(:active) md-ripple {
  opacity: 0.12;
  transition-duration: 105ms;
}

initial thought is to use this map.get stuff to provide handling for the ripple which could be set here. Gotta do some reading about this though, my knowledge about scss is limited

Edit: went with @import ripple.controls: ripple.controls

Seems to work pretty well (I'm still testing around).
One side-effect is that the ripple animation wont work (the calculated stuff), though im not sure if thats needed for such small ripples... if it is needed one could probably check if pressed came from the AttachableController or the label.