My understanding - at least for the original Pi - was that there was a design flaw where the sd card was not protected from power irregularities in the same way

My understanding - at least for the original Pi - was that there was a design flaw where the sd card was not protected from power irregularities in the same way the rest of the device was. There's a lot of argument over whether it's a hardware design flaw or a problem with sd cards generally (perhaps the usb spec has better buffered writes or something)... It's apparently much more a problem for long-running applications with high write frequency.