The national MUTCD always shows interchange sequence signs in the median. I'm not aware of any jurisdiction with policy for locating such signs on the outside.
What would make sense is if Caltrans moves the interchange sequence signs to the outside in cases where there is a buffer-separated or barrier-separated HOV/HOT lane... but that is not the case here.
The California MUTCD also requires that interchange sequence signs be in the median (Section 2E.40-09). But I've seen a bunch of instances where Districts 07 and 12 have been pulling interchange sequence signs from median overhead sign gantries, installing outside shoulder sign gantries, installing the new interchange sequence signs there, and then pulling down the median gantries, leaving the median gantries empty, or repurposing median gantries for HOV lane signs.
Here's an example. They pulled the sign off the median post and installed a new one behind the soundwall on the right on a new gantry. There are lots of these on the Artesia Freeway. When they've done this, in some instances they leave the median gantry empty. In one instance they installed a Carpool Lane sign in its place. In another instance they left both the old interchange sequence sign in place on the median gantry and installed a new shoulder sign gantry in the same location with another interchange sequence sign on it.
Here's another example. When they widened the 22 freeway, they did not replace the existing median gantry and instead put a gantry on the outside shoulder. Although almost all of the interchange sequence signs on the pre-construction 22 were in the median, I cannot offhand recall a single instance where they put the interchange sequence sign back in the median after reconstruction.
If anyone knows why they did this/are doing this in violation of their own guidelines, I'd love to hear the explanation.