It's not just fat utilization but also glycogen, a chemical resembling starch that is stored in the liver and also directly in the muscles. I don't know the ideal conditions for doing so, but the muscles can be "trained" to store more glycogen. (In part this is what causes muscles to "bulk up".)
Presumably training in conditions where the blood glucose level is low would help to "train" the muscles to store glycogen, though this would be a long-term thing, over months, not something to work on a few days before a big ride. And glycogen is important not only because it can help to fuel muscles several hours into a long ride, after blood glucose is exhausted, but also because it can help provide "peak energy" even when one is well-fed.
(Note that burning fat directly in the muscles is quite inefficient and can lead to "ketosis", causing a sense of fatigue and loss of mental acuity. Fat is more efficiently "burned" in the liver, but the rate of fat processing by the liver is insufficient to support a sustained high-energy effort.)
It needs to be remembered that there is a lot of really crappy advice out there, often from "experts", re nutrition. Probably 80% is bogus. In particular, many "experts" who talk about "burning fat" have probably never even heard of glycogen. My "expert" opinion is informed by having a genetic disorder (myoadenylate deaminase deficiency) that affects how muscles use energy, so I've taken interest in these topics for decades.