I took a look at the brief entry for 'John Woodcock' in Anderson's GMB2 (6:510-511). For John Woodcock of Rehoboth specifically, he uses the Dedham Historical Register (1893), and a Farr genealogy (1959).
The Dedham Historical Register includes a genealogy of John Woodcock, and leaves Sarah's last name as blank.[4:173]. The Farr Genealogy however gives her name as "Sarah (Curtis?)" [322]. The sources included at the end of the Woodcock section in the Farr genealogy include the above Dedham reference, as well as:
• some vital and parish registers (the only applicable one for Sarah was her recorded death in Rehoboth [900]) "Sarah, the wife of John Woodcocke, the 10th of may, 1676")
•Ligget's Hist. of Attleboro (I can't find this source - perhaps it's a mistype of the next source - Daggett's Sketch Hist. of Attleboro?)
•'A Sketch of the History of Attleborough', which on p. 90 mentions wife "Sarah"
•'Genealogical and Family History of the State of Maine' [3:1335], which mentions wife "Sarah"
• 'Early Rehoboth', [1:56], [3:62]. The vol. 1 source is a 1689 list of inhabitants (John Woodcok senr), and the vol. 3 source is a mention of the garrison house - no mention of Sarah.
The above source on other pages mentions Sarah Woodcock in relation to deeds, a 1650 (sic-should be 1660) deed [3:153] (original deed book - right, bottom), and a 1673 deed [3:162], (original deed book - right). There is no mention of a Curtis in these deeds, though I have not looked exhaustively.
It seems like Sumner's Farr Genealogy is the likely source of the name "Curtis", though the fact that she writes it as "Curtis?" makes me think she was researching the possibility, or perhaps she received some letter from some correspondent giving her name as such? There is no source (unless it is in Ligget's book, if it exists) that she cites which gives the name "Sarah Curtis".
Why she was linked to William Curtis I don't know - possibly because of the baptism of a Sarah Curtis?
