1) Fructose intake refills liver glycogen, not muscle. The recommendation to get some fructose before the depletion workout is to prime the liver for the upcoming carbs. Basically, warming up the engine.

2) Ketosis is controlled by liver glycogen, not muscle glycogen. Muscle glycogen is only used for powering the muscles themselves.

3) Even if you take some fructose, you'll likely still be in ketosis. Also, the body doesn't run on ketones. It will run on either fat or glycogen. The brain will run on either glucose or ketones.

For some the carbup serves to stop the metabolism from slowing. The carbup serves to over-fill the muscle glycogen, reportedly providing more support for intense resistance training.

From the CKD place.