There was one silly code leftover from 5.3 development in ConfiguredActionbarSectionDefinition, which I tentatively removed ahead of 5.3.2, but had to revert back:

    public void setAvailability(AvailabilityDefinition availability) {
        // FIXME This is plain wrong, availability for multiple selection matches sections for which it is not configured (i.e. set to false)
        // But we have to keep it for the time being because some content apps rely on this incorrect behavior.
        ((ConfiguredAvailabilityDefinition) availability).setMultiple(true);
        this.availability = availability;
    }

In essence:

• availability for multiple selection matches sections for which the multiple property is not true (i.e. non-exisiting or set to false)
• but many content apps (+ UI tests) rely on this incorrect behavior.
  • e.g. contacts, categories do have a multiple section configured, but they don't even have an availability subnode with multiple set to true.
  • When trashing the silly line, one can end up with en empty action bar.

As a result, currently we always fall back on the first configured section — typically the one dealing with singular item selection — so the set of actions displayed, their labeling and the section title are all wrong.

Side note: multiple availability does work correctly on individual actions; most of them are expectedly disabled when selecting multiple items.