In theory it does. Unfortunately, I've never been able to get it to work because the way in which it obtains a hardware ID to tie playback to doesn't work on the Linux distro I use and I can't feasibly debug or fix it. Assuming it were actually secure as stated, the Mozilla solution would have the same problem - if you can modify how it obtains the hardware ID, you can bypass the DRM in ways that content providers wouldn't accept.

(The really stupid thing is, I was trying to watch online streaming video that was available to the whole of the UK, with access controlled through IP geolocation. There was no need to tie decryption to a particular device ID in the first place. EME seems to be taking exactly the same approach though with support from Mozilla.)