Ok- after beating my head on this for hours today to no avail, I took a break after posting this cry for help. This time when I edited the wall type, I realized that the framing override can be applied individually to each layer of the wall (regardless of what type of material it is). The default is for the top layer on the list, whereas in my case actual framing was the fourth layer. Overriding framing here fixed the issue.
I’m still curious to know why the program was drawing studs at 24”oc instead of the 16” I specified in the defaults….