There are serious shows that have successfully recast major actors into different roles (see Dillahunt in Deadwood) but everything about him was radically changed to the point he was practically unrecognizable, which is the opposite of what happened here. Every scene with Christina was purposely evocative of her past as Dolores, from her very introduction, waking up the same as Dolores did. Painting like Dolores, writing stories similar to Dolores' loops, using similar phrasing as Dolores' programmed speech, Teddy...
Vs, again, Dillahunt, who as Wollcott was purposely presented as far from Jack McCall in camera framing, wardrobe, speech, and general appearance as possible without surgery.