It sounds like you're trying to "hint" at the idea that a bunch of games are using Epic Online Services and/or the Online Subsystem Steam API associated with it, but beyond that I don't understand what point you're trying to make.
If you're trying to obliquely cite that as some kind of counterexample where it's reasonable for a game's source code to remain secret just because part of it is that library, then no, it fucking isn't. I can't tell whether EOS has the source code available along with the rest of the Unreal engine or not, but if not, it ought to be and IDGAF about any excuses Epic might have for not making it so.

LOL, what? You're the one trying to make a point here, not me. Spit it out. I'm not gonna do your fucking work for you!