I don't think it really mattered to JtR how he rendered them unconscious as long as they got unconscious. Dead or unconscious, didn't matter, as that was never the focus of his attack, just a means to an end. So the MO here can deviate quite a bit.
In Nichols case it looks like she has been punched out cold first. Chapman seems to have gone the same way. Schartz literally describes Stride being hard slammed into the concrete. Thrown down. Not pushed down. All of this stuff seems like pretty random violent blitz type attacks done when the victim is off-guard. MJK may have had a sheet pulled over her face before she was killed. There seems little in the way of there being a solid pattern in how the blitz is done, but the brusing to the face, neck and chest shows it was done and there is some.
Tabram was stabbed in the throat. She was not slashed. So that isn't really like JtR.
However the time/location and position of the body is all in line with JtR. There is obviously some attempt at sexual mutilation, like Nichols.
I postulated awhile ago on the board that the positioning is not completely sexual at all, but aids exsanguination, like someone who was feeling faint, putting their legs up helps blood flow back to the head while on your back.
As correctly stated, Tabram's death is all odd and strange. The stabs to the neck may not have been enough to kill her. Maybe the killer thought she was dead only to find her coming too during the mutilation and then having to strangle her to finish her off. So that's a mistake he won't make again. No more stabs to the neck. Next time he slashes.
What I am getting at is that it doesn't seem to matter to JtR what killed them as long as they where horizontal, unconscious and where not going to bother him any more.
Bona fide canonical and then some.