Since I do not want to escalate this any further, I want to kindly ask which or what parts of the paragraph in question is actual speculation? The paragraph states only facts for as far as I can see. It literally summarizes what we do know with references to the fight between Cinder and Raven to Ruby using her Silver Eyes against Cinder, which are all things shown in the actual episodes, thus not speculation.
So please, tell us what you see as speculation so we can elaborate.
The paragraph nowhere states that such thing isn't unacknowledged, it just isn't there. Something not being there does not equal to something being speculation. Salem using magic to summon those arms does not confirm that it is the same method that sewed Cinder's Grimm arm to her body? Maybe there are more methods to applying a Grimm arm to a person?
Just because Salem did it to summon individual arms, does not confirm that it was the same method used for Cinder.