For clarity, I am currently downloading a video onto my MicroSD card from my Android app. So yes, "SD Card" is generalized to "external storage". I have no idea what the consumerist.com write-up means by "The feature doesn’t support any and all Android devices that have a microSD slot, either".
Fixed the quote for you.
I guess what this means is that there are some devices that can't use SD. I don't know what the constraints are... maybe it only works on devices with sufficiently-good hardware DRM (there are various levels, and Netflix does adjust its behavior based on what your hardware has), or maybe it only works if the SD card is configured as adopted storage (which is encrypted for security, making it also unusable for sharing Netflix videos). Or maybe The Verge is just wrong and it does work on all devices. Or something else.