I forgot to add that not only will they change "currently playing" every 3 secs, also the cover art of each series changes, as an A/B test. So if you use that as a visual confirmation, well tough luck.
In the case of Netflix, there's a reason for all of this. They don't really want you to go and sniff around the catalog in easy ways. You might discover its not great. Best to throw a bunch of random stuff in your face to give you the illusion of a fabulously rich and "dynamic" experience.
The distraction UX of Netflix is intentional. In the case of Spotify it's mostly incompetence.
But if you are interested in the why of "currently watching" moving all over the place, you'll notice its harder to find the longer its been since you opened netflix combined with the faster you start looking for it.
Different part of Netflixes backend respond at different speeds. The call for "Top in the US" is likely cached and up to date, the call for "What did dataengineer56 stop watching" is probably cold and slow.
This leaves netflix with a few options, and what they seem to have settled on is "Show everything that has loaded, and quietly insert the stuff that loads later into parts of the screen the customer isn't looking at, so our entire app seems to load instantly"