`{{content-for}}` hook of addons is not invoked

I've been trying the support for addons and worked like a charm except for this little detail.

Example with ember-power-select: https://ember-twiddle.com/b076c42b8529f3f95165dca5c82abef3/23f8fbca074bb26605b35448dd909453edf8b7f0

Apparently the `content-for` hook of the addon is not invoked, and therefore the destination div for ember-wormhole is not attached to the page automatically.