Access Control isn't my "thing", but from what I gather, your assumption is correct.
Previously, most access-control devices communicated over a RS-485 or similar bus. IP-based access control systems communiate over an Ethernet network, allowing you to more readily standardize on cabling, use commodity parts (switches, etc.), and do move/add/change stuff more efficiently.
Unlike cameras, where IP allowed for higher resolutions more easily, I don't think the average access control system suffers from a lack of available throughput, but I do think the RS-485 network concept can seem a little dated and harder to troubleshoot in a modern system.
So, (and again, I'm not an access control guy), I don't think IP-based access control systems open up as much new potential as IP-based cameras systems did, it's a little more of a convienience/standardization move.
Brian Rhodes would probably have a much better perspective.
We will typically separate what we install with Edge IP Access Control devices (HID Edge EVO, Axis Door Controller would be examples of this), vs when we install or replace "panel" architecture systems that have 1-2 main controller devices that have a network connections and a bunch of 1-2 door controllers that are connected separately with serial connections.