Now, I am not sure you are right, but if indeed he is a SK that kills pairs, and if Lyric and Elizabeth were his doing, then I am positive he has OCD related to symmetry (you know, when you step over cracks in pavement with R, and next time, L, foot, or go up the stairs making equal amount of steps with R and L foot).
These two pairs of girls look similar, pointing at this symmetry. One, lighter and younger, another one, bigger and older.
Is he going to look for a couple slightly older than Libby and Abby next time? Like, 17 and 18?
Also of the same physical type?
And if the girls were in any way posed, I wonder if Lyric and Elizabeth’s remnants were placed the same way as Libby and Abby (I don’t know how, but for example, the larger girl on the Left?).
I am not sure BG is a SK and killed both couples, but if he did, there might be some “symmetry” analogy there.
He may not necessarily kill couples, but probably has “lairs” where he’d bring two bodies with the same physical characteristics as the girls, and place them in a certain way.
MOO.