I think this refers to the k factor, that puts the "soft limit" on decentralization. This I see as a barrier to entry: Ethereum 2.0 is 32ETH and that's it. Cardano has no monetary fee, but has eventual competition between pools, which is variable, likely ongoing cost. Barrier to entry is less defined, and could at some point grow beyond dollar value of 32 ETH (to become a competitive pool). Whereas Ethereum 2.0 will always stay a constant 32 ETH, no matter how many validators exist.