See if this excerpt from another recently written review paper is clearer to you: https://link.springer.com/article/10.1007/s10876-021-02031-6
[...] For producing hydrogen [Rydberg matter], another aspect must be considered. The catalyst must also be able to chemisorb the hydrogen gas molecules. More reactive metals bind the atoms stronger to the surface, but this also means it is harder for the atoms to desorb, often leading to a volcano plot for useful catalysts . Though the desorption of the Rydberg hydrogen atoms should be assisted by the formation of clusters, meaning it might be possible to use a more reactive catalyst.
Ref. 49 is: "T. Bligaard and J. K. Nørskov, in Chemical Bonding at Surfaces and Interfaces, 1st ed. (Elsevier, 2008), pp. 255–321."
To make another example: carbon alone does not dissociate hydrogen to atoms, but hydrogen atoms dissociated elsewhere can easily migrate to and desorb from carbon surfaces. Carbon works for points 2-3, but not at all for point 1. So you would need also a suitable metal surface for that, as suggested earlier. Metal catalysts supported (deposited) on carbon also already exist commercially, however.
This could be a related topic: https://en.wikipedia.org/wiki/Hydrogen_spillover
I think it should be nice to more deeply theorize this "post it " expectation, no ?
Hydrogen bound to metals in the form of a hydride is not readily available for the clustering process (RM, UDH) proposed by Holmlid and colleagues.