I think you misinterpreted a few view points. Otherwise it would be a sound theory and very well set up. "The worm says:" means that it is the one speaking. Which is very similar to the way ahamkara bones work. A lot is speculation for now until more lore is a available, but the ahamkara and worms are definitely related in their natures.
I think you're referring to this part from V: Needle and Worm: "It’s dead, but it still speaks to me. It says: listen closely, oh vengeance mine..."
I wasn't claiming that those were Sathona's words, only that this is Sathona's account of what the worms spoke. This is just to illustrate the the worms indeed speed in the "oh ___ mine" pattern.
On the next example I gave though, it's definitely Sathona speaking when she says "Let us dive, oh sisters mine." (VIII: Leviathan). This illustrates that the worms can change the speech of those they influence, in this case it is Sathona who is in their influence. I am claiming that like Sathona, the Ahamkara are also in the influence of the worms.