That's all true in the context of trying to boost voltage/clock speed on a chip that is already running close to thermal limits when using a stock active heatsi

That's all true in the context of trying to boost voltage/clock speed on a chip that is already running close to thermal limits when using a stock active heatsink (which are already huge). And yet, even in that context people are able to overclock parts rated for 3Ghz to over 5Ghz using extreme cooling solutions. In the context of building desktop-grade ARM CPU's we're not talking about 5Ghz overclocks, but about going from passive cooling in cramped space without any airflow, to something more like a laptop or workstation with active cooling. You also don't need to go all the way up to 5 Ghz, the A12X for example runs at a maximum clock speed that is 40% lower than the base clock of the i7 the benchmarks the article is referring to, yet it manages to be already quite close in terms of performance.