Good stuff if it's true. If there was such a will of Thomas Staineridge, naming two of his sisters, one of them Ann Witham, plus the other supporting data l, then yes l, I'd say there's strong evidence for Staineridge as her maiden name. I'd feel more comfortable seeing the original text or at least something published in a peer reviewed journal (vs a transcription on a worldconnect profile that includes no source citations) .
Conversely, we should not rule out the possibility that she could have been a half sister. Same mother as Thomas but different father.
Do we have any idea where the Hoag/Hogg claim originated?