Note: I have never experienced this with PvE so I am assuming you're talking about PvP as thats where it normally happens.
No they have not changed it. Thats the stun lock/chain people manage by the sounds of it. You are supposed to have immunity after a stun which I believe lasts for 3 seconds (an eternity in pvp)
I.e You get stunned by javelin but then also at the same time get stunned by another knock back and another.
From my understanding this is caused by the fact that the CC aspect of each stun isn't counted if there is a knock back involved prior to the CC but built into the ability. So basically the stun doesn't count until you hit the ground but it still forced you to break free because you can break free from a knock back. Knock backs and stuns are weird and are separate things both are CC and both are annoying as hell in this game just based on their interactions alone with animations and input delay from the user and the receiver. Knock backs aren't counting, actual stuns are (reverb as an example).
This is why Templars can jav spam and successively knock people back 3 times in a row without procing immunity on the player because the stun hasn't fully registered yet (no people this was not fixed contray to popular belief it still happens).
That said, it can also be that your client is registering the stun but their servers are not so the server doesn't register your that you've been hit but you still need to break free anyway and thus you aren't granted CC immunity. This happens a lot with lag and such from the servers... but this is theoretical because honestly PvP is a mess due to server performance.
ex: when I was bombing, I got stunned and broke free but I then desynced and got stunned again cancelling my tether (yeah delays on ult casts were a real good idea weren't they ZoS? -_-) so I just ended up dying when I should of had CC immunity.
Edited by xeNNNNN on February 21, 2020 5:50AM
Ah, e-communities - the "pinnacle" of the internet............yeah, right.