I don't entirely understand the permanent residency for EU citizens part. As far as I understand, EU citizens have work permits and no restrictions on residency in all European countries, what would permanent residency get you on top of that?
The "free movement of labor" in the EU isn't a completely free right to live anywhere and be treated as a resident. Every EU citizen has the right to reside in another EU country for up to 3 months for any reason, and to be hired without having to apply for a work permit. But after 3 months they must register, subject to certain restrictions of the host nation, usually that the person must either have employment, be a student, or be able to show that they have sufficient funds to support themselves. In that case they get a temporary residency status that allows them to live in the country and be treated as a resident for certain purposes (such as healthcare).
Permanent residency removes any qualifying requirements, and gives the person the right to remain indefinitely in the country with full social rights (except voting), as if they were a citizen. That means, for example, that they would be eligible for the national healthcare system and state welfare system even if they found themselves long-term unemployed, which isn't normally the case for citizens of other EU countries.
