Okay, let's break it down.
Firstly, the term breaking the third wall hasn't been widely accepted yet, but let's go with it.
Your second link should be taken with a very critical eye. See how it mentions breaking the first, second and fifth wall as well, which isn't established terms and when you look them up, the few that are speaking of them are saying different things. This discredit the author of the article a good deal.
Your first link is better and it essentially defines the break as this: When a character addresses the medium.
Now you are running into a problem, because Ava isn't addressing the medium, she doesn't acknowledge she is in a game. She is speaking directly to the MC and while it may seem pointless, because he can't remember afterwards, that actually is the point. She is evil and can tell him her plan without him being able to defend against it. It is a power play. Remember the MC did the same thing to Scarlett. Making her aware, but unable to stop the process of her getting enslaved. A power play and revenge for the MC. Ava is doing something similar, we just happen to experience it from the victims side now.
As for it being a plot hole, well a plot hole is then there is inconsistency in the story or something is contradicting. This doesn't happen here. Not only doesn't the event contradict anything, if you look at Ava's behavior before, it falls quite in line with her already shown personality.
It is even more hilarious, when you realize it fixes at the time a presumed plot hole. Multiple people were saying that the way you tackled Bill's problem would be suspicious and was a stupid way to fix the problem, but it turned out that was actually Ava's intend, because she did want to raise suspicion and get caught. So the previous actions made sense, we just didn't know it at the time.
