Dr. Phillips. - I have not noticed any sufficient similarity to convince me it was the person who committed both mutilations, but the division of the neck and attempt to disarticulate the bones of the spine are very similar to that which was effected in this case. The savagery shown by the mutilated remains in the Dorset-street case far exceeded that shown in this case. The mutilations in the Dorset-street case were most wanton, whereas in this case it strikes me that they were made for the purpose of disposing of the body. I wish to say that these are mere points that strike me without any comparative study of the other case, except those afforded by partial notes that I have with me. I think in this case there has been greater knowledge shown in regard to the construction of the parts composing the spine, and on the whole there has been a greater knowledge shown of how to separate a joint.
I've bolded the relevant parts.
He's not agreeing that Mary Jane Kelly's leg was severed. He doesn't correct the coroner on that point but he doesn't mention the leg at all. The only specifics he mentions as being similar are related to the neck and spine, not to Mary Jane Kelley's leg.
It sounds to me like either he didn't remember whether Mary Jane Kelly's leg had been severed so he didn't mention it, or knew from his read that it hadn't been but forgot to directly state that.