Maybe, maybe not. I might include it one day, but here's my rationale about it.
Before the Mask: The Return of Leslie Vernon connects to the Saw franchise. John Kramer appears twice and has a lot of dialogue with Doctor Halloran. He states he's been a killer for a decade, presumably between 2004-2016, supporting the comic's 2017 placement and contradicting #3's 2008 date. However, due to his certain death in Saw III, his cancer, and the way the comic portrays slashers being talented individuals with lots of prep-work rather than legitimate supernatural killers, it might be best to overlook this for now and say that the Slasherverse's John Kramer is a variant, especially since I believe that Freddy, Jason and possibly Myers are intended to be people who latched onto the legend of the real Jason, Michael and Freddy. Michael could be the same guy I suppose, Freddy is possible but unlikely, and Jason is certainly not the same. John Kramer is definitely the real John Kramer of this universe but I don't think he's our John Kramer, the one that mentored Amanda and Hoffman, the one with cancer, the one who was killed in 2006.
Obviously due to connections to Behind the Mask in Friday the 13th: The Game and Hatchet II, Leslie Vernon IS canon to the Slasherverse. Using Friday the 13th as an example, it just means that there's a real Jason who drowned and came back to life as well as a fake Jason who, like Leslie, latches onto the legend of historical events in order to push a narrative. Real Jason doesn't give a toss about "survivor girls", "Ahabs", and all that attention-seeking nonsense. Fake Jason, who is the one that knows Leslie and Eugene, looks like Kane Hodder. He holds the same values as Leslie and Eugene. In a way, he's exactly like Roy Burns in Friday the 13th: Part V: A New Beginning. He's able to mimic Jason perfectly.
You could say this interpretation throws Hellraiser into question, but... oh well. There's the Chucky and Pumpkinhead connections, plus Hack/Slash's K-O seems based off of Pinhead's design.
