I don't think that's true, I had several kindles and it was a paper white that looked like it was micro USB, and charged fine on an alternate cable, but would not do direct USB connection on anything but the kindles own cable.
I'm pretty sure that that's incorrect. I worked at Amazon, on Kindles, and we used retail units with whatever random USB cables we could scrounge up, on all of the various Kindles (fire and eink). I also can't find anything on google mentioning it, and just tested with my own (non-Amazon) cable on my own retail paperwhite from 2015.
You may have just had a cable without functioning data lines.