You only get a response back from the Regedit command, that sets a key value into the registry. The Powershell command to force-run the scheduled task just returns right back to the prompt with no response so it looks like it did nothing, but that's normal.
In the end, I'm not really sure if missing the 2023 KEK key is all that serious since you have all the 2023 keys in DB, suggesting they were signed using the (currently unexpired) 2011 KEK certificate. This makes sense if the purpose of the KEK is to validate any keys going into DB. It may only be a problem in some distant future should you want to append DB with a new key that can not have been signed with the (by then expired) 2011 KEK certificates. But how likely is that?
So my theory about why the KEK can't update:
In order to update the KEK it has to have been signed by the PK, or Platform Key, which supposedly you own but Dell actually does. It could be Dell never allowed signing a Microsoft 2023 KEK with their PK so it fails. (So yes, Dell screws you over here... is that a surprise?) But since Microsoft can still sign the DB keys with the 2011 KEK they keep you rolling. That's just a guess on my part, but fits what I've read of how the Chain of Trust back to the Platform Key works.
The good thing about MOSBY is it replaces the Dell-owned PK which is shared by the all the systems they build with your own unique in all the world PK it generates as you update the keys. So you've just taken true ownership of your system