Just jumping in to confirm the above....
Prior to the recent HR Renewal feature pack, "dynamic actions" were NOT supported/used/mimic/etc with HCM P&F. By using clever custom generic services and rules or simply have some custom workflow task call a custom ABAP method, we could achieve the same result.
However, SAP has been working on this and there is now "some" solution for it. It is VERY early so I would suspect it is still limited and/or buggy. As I absolutely loathe dynamic actions (they are OLD technology that was good in it's time but its time has LONG gone), I am hoping they do not put too much into them and try to sunset dynamic actions all together.