Charlestown, MA: Francis Griswold vs. Francis Grissell

In "The English Bullard Family Revisited," by Stott & Hyde, NEHGR, 154:178, footnote #27 states:

"Mary [who married William Bullard] was apparently widow of Francis Grissell of Charlestown as shown in
a deed from Jonas Palmer and Elizabeth Palmer, both of Rehoboth to William Bullard of Charlestown, 9 Nov 1655 (Middlesex County Deeds, I:152 [FHL microfilm 554000]). Francis Grissell died in Charlestown on 2 Oct. 1652."

Then, footnote #27 states:

"Dean C. Smith in Ancestry of Eva Belle Kempton [note 2], p. 205, erroneously calls Mary [who married William Bullard] widow of Francis 'Griswold'of Charlestown."

This implies that the authors do not believe that Francis Griswold = Francis Grissell. but they do not explain why they think this way.

Can anyone shed light on this please?

Thanks!