I believe my memory leak is caused by PlayReady DRM. Leaving it paused for just 5 seconds makes it go to 500MB while on Chrome it's 166MB. Going to edge://flags to disable PlayReady DRM means that Netflix content doesn't play, probably because Netflix is using the user agent and expects Edge to have PlayReady.
Microsoft Edge Insider supports PlayReady DRM technologies. Thus, Microsoft's PlayReady DRM, Insider Edge will be able to to play Netflix videos at both 1080p HD and 4K UHD resolutions. Other Chromium-based browsers (Google Chrome, Firefox, etc.) can stream up to 720p using the WideVine DRM technology.
With the higher resolution, I suspect the delay and 500MB you are encountering is for buffering so you don't experience any lag/stutter during playback.
Being I am not 100% sure in my hypothesis, I'll submit this as a bug to verify.
@pneenkoalabear I guess you should check how's your memory after watching 30 min of movie and then checking again after watching a full hour. If the memory use is almost the same then it's not a memory leak!
It uses up 190-230MB. Still more than Chrome though :( at least it doesn't go overboard
On Edge UWP:
I was able to play a video but it was using up 280-330 MB which is quite a bit compared to Chrome Canary but as Darren said, it is playing at a higher resolution with DRM too although it used up that much when browsing and not playing any videos. Unlike Edge Chromium, Netflix starts using up memory really quickly but thankfully doesn't go any further than 330MB.
@cbomtempo Were you able to play Netflix content at the time of the original post?