Warning - graphic content follows.
I agree incineration is not an easy thing to do, nor is it common. However, a few threads upstream, we were kicking around the theory that as a physics student, he probably had access to various labs throughout campus. Once students are finished running tests in labs, how do they dispose of the physical matter used in the testing? Is any of this incinerated?
We have to remember
several weeks passed between the time YYZ was abducted and BC's arrest. While incinerating (or chemically destroying) a body may be difficult, it is not impossible. Bodies can be dismembered and disposed of piece by piece. I'm thinking Ed Gein, the model for the serial killer in "Silence of the Lambs" and "Psycho".
Lastly, Ed Gein lived in Plainfield, Wisconsin, which is a stone's throw from Stevens Point, Wisconsin, which is where BC was born and where he went to school. (I believe the distance between Stevens Point and Plainfield is between 20 - 30 miles).
I grew up in Central Wisconsin; Plainfield is about 45 miles south of where I was born and raised. Even though Gein's crimes took place before I was born, his name and crimes came up in discussion occasionally.
I've included a map, where Plainfield's location is marked by the red balloon. Go due North on Highway 39, past Plover, and you'll see Stevens Point.
https://www.biography.com/people/ed-gein-11291338
End of graphic content.
Just MVHO.