But while they've demonstrated a low-energy way of computing an equivalent hash, presumably this is in no way currently competitive. Therefore this proof-of-concept itself is not an example of an algorithm with capex-dominated costs.
Given that capex versus opex is primarily a matter of accounting (i.e. do I buy a PC, or do I rent a VM from AWS?), I don't understand how that algorithmic distinction can even be achieved. If the ongoing cost of running the device become negligible, then you just incentivise the miners to "spend the saving" by buying more mining devices up-front.