Ball spin adjustment is not available on every shot. Sometimes it works and sometimes it does'nt.
That has always been true- partial spin shots are a bit of a crapshoot, although full bs or flat setting are usually consistent, in my experience, ie within the parameters of VEM. Whereas, for partial spin shots, as you say, sometimes it "takes" and sometimes it does not. For this reason, on full shots (other than wedges) I prefer full backspin approach that at least covers the distance and then reduce power as needed.