Key rooms with multiple entries

I'm trying to find out more about how this works.

When the game first launched, if you unlocked a key room door it turned ALL of the doors to that room green.

At some point it changed so that only the door you unlocked turns green, and the rest remain red.

So does that mean the other red doors are still locked? Or can someone just walk in?

Today I went to Spaceport North trench tower and someone had beaten me too it. I checked both lower doors (very poorly) and didn't notice that one was green, so I thought nobody had been in. I snap hooked to the roof and went in the top (still red) door to remain discrete. Once inside I saw that it had been looted already, and then noticed that one of the lower doors was in fact unlocked and green. Thankfully whoever used it had already left.

I was able to walk in the roof entrance but I'm not sure if that is because I had the key. It did not consume the key, so I used it at South Tower instead.

I saw an Gaming Merchant video where he entered one of the trench towers holding 2 keys, entered one door and exited the other. When he exited it used up the second key, but it may well have been a bug.

Does anyone have the actual facts about how this works? It would be nice if the remaining locked doors stay closed to intruders but I don't know whether to trust the red door status.