I think it's a good rule of thumb. When they send robots into something like the Fukushima site they don't last long.
My first take is that I'm not surprised from a fermi problem standpoint that you can destroy two computers made from small parts smashed by radiation with a similar dose. But maybe that intuition is wrong because your brain could survive losing a few neurons but a microchip could be 0% functional after losing one transistor. My rule of thumb is about right for conventional chips but you can certainly get rad-hard chips that hold up better:
