The beat writers still have Walker listed as the 12th pitcher pretty consistently. And also think they might go with 12 in the longer series. I think Walker still gets the nod as the mop-up guy. If they go to 13 for NLCS then Lazar (or Turnbull if he's ready, or Gilbert) could slot in ahead of him.
Last year Lorenzen (the 12th guy) pitched 1 inning in a 10-2 NLDS win and 1 inning in 5-1 NLCS loss. The 13th guy, Walker, pitched not at all. Wheeler made one relief appearance in NLCS.
In 2022 the 12th and 13th guys were Kyle Gibson (2 appearances) and Nick Nelson (1 appearance). Ranger and Thor both made two relief appearances.
No matter how many arms you carry they are pretty negligible roles. If anything there is more pressure on Banks and Ruiz because we can't count on the #3 or #4 starters to be available in relief (though neither Falter nor Sanchez pitched out of the pen in '22 and '23, not that we would have wanted them to).
I imagine we'll see a lot of Hays this weekend but I still wouldn't start playing him against RHP regularly.
The roster this week doesn't have to be the same as the playoff roster either of course. I do think Clemens is the better bat, but if their thinking also involves defense and two-for-one moves Stevenson isn't necessarily done.