As always, my problem with that logic hinges on the fact that, in my mind, LISK is the person who murdered the GB4, and not necessarily the person responsible for these other murders. LISK took a strange kind of pride in the bodies of his 4 known victims, imo. All four known victims were a particular physical type, all were strangled (not dismembered, and not mutilated), all were left intact, all were wrapped in burlap, and all were placed within close proximity to one another. I would bet ANYTHING that there was some kind of physical marker near these bodies that allowed him to pick out exactly where the bodies were. I think he watched this site often and got off on the power he felt knowing the bodies were there. Now, all this is just my opinion, of course, but I've lived with this case for years now, and I can't un-know what I think I know at this point. Perhaps that's a huge mistake on my part, but it is what it is.
So...from that perspective (right or wrong), I don't think LISK chops up his victims. I don't think he kills just to kill. There's a process involved, imo. Pick them out, court them, kill them, place them in a trophy case, revisit, and admire the end result of all his work. Shannan doesn't fit that pattern...she's too messy (for lack of a better word). If we remove what we know about Brewer and Pak from the night Shannan disappeared, all we really have is the body of a woman who was an online escort, found partially clothed, in a marshy area off Ocean Parkway. The only way I could see Shannan being a victim of LISK is if I consider the fact that something must have gone terribly wrong for him with this particular victim. But, in this particular mental game LIN has set up for us, I know nothing about the 911 call, Brewer, Pak, or CPH. I have nothing to tie Shannan to the four known victims of LISK. Hell, I don't even have a cause of death to link them. So, no...I wouldn't automatically assume Shannan was the work of LISK.
All just my opinion. (And not very well written, I'm afraid, because I'm still working on my first cup of coffee.)