Parent is not talking about the percentage of photons that are translated into charge, but about the amount of charge that can be held on a given area during exposure without saturating & spilling over to surrounding pixels. Deeper electron wells with the same amount of readout noise would increase the dynamic range of the image; I don't see how we can deduce that this was the stated benefit from the article though, or how that benefit could even be recognized given the early stage of the technology.