This came up once on Facebook. I don't recall if you participated in that conversation. As I explained then ... that is the maximal rate of oxidation of lipids which is something entirely different from the maximal rate of release of lipids from adipose.
Right now, with a full belly, body fat is not your only source of energy. You have a steady stream of giant lipoproteins (chylomicrons) currying lipids from your gut throughout your body delivering their payloads to your cells, and they have been for several hours. Your liver is scooping up lipids from circulation, packaging them into low density lipoproteins and sending them throughout your body delivering their payloads to your cells. And of course if your insulin is low enough your body fat is releasing energy at the rate of 290 kJ/day for every kg of body fat. Your cells can also store energy in lipid droplets so they are not normally rate limited by adipose.
This explains how your cells can burn more energy when under load than your body fat can release for use.
BTW the actual maximal rate of lipid oxidation is apparently limited by the rate that we can transport lipids across our cell walls.
Prior to Jeff Volek's FASTER study, it was generally accepted that the rate of maximal fat oxidation is predicted by VO2Max (aerobic fitness), Gender, and Exertion but not body fat - and is 1g/min with most athletes in the range of 0.45-0.75 g/min.
Jeff Volek was able to show that athletes who have become adapted to fueling on fat can oxidize energy at a rate previously thought impossible at 1.1 to 1.8 g/min. One key adaptation is an upregulation of the MCT transports, and a downregulation of glucose transports which could account for that.
The fact is however that these athletes were not fasted. They all had a high fat milkshake before getting on the treadmill and getting their needle biopsies.
If you fast for 10 hours, then you won't have any lipids circulating in chylomicrons from your gut. Now if you fast longer and your energetic demand exceeds you adipose supply, you will draw down on lipids circulating in LDL, and at some point you will be rate limited by how much energy your adipose can deliver - which is a factor of your fat mass (minus insulin's inhibitory effect if your fasted insulin is high), and roughly 31.5 kCal/lb Body Fat.
So if you have 20 lbs of body fat, you might think you have access to 3500 kcal x 20 = 70,000 and it is true that you do have 70k in your account but your daily ATM transaction limit is only 630 kCal/day.