It appears Alien Theory is trying to counter claim it. Even going so far as to pretend to not only not know who could be resonsible for the strike but has the audicity to actually say this:
"This video is my own original work using my own scripting, editing, and presentation. The title of my video and the claimed article are similar. The subject matter is the same, summarizing plot elements and character details derived from the "Alien" series of films and video games. None of the actual sources of this summarized information are under claim, only a "Fandom Wiki" article with similar wording to both those other sources and my video. I believe this claim was either made in error, or it was filed as an act of bad faith in order to abuse YouTube's copyright protection system in order to negatively affect my channel. I do not know who the claimant, known only to me by the provided email"
There is more beneath this but it features his personal information and I'm not a doxxer or whatever they call it these days.