I know that the article talks about how counting calories isn't necessary on OMAD, but I just wanted to throw in my personal experience for consideration.
My dietary world was flipped upside down when I learned about the concept of caloric deficits a couple of years back. The simple fact is, you lose weight when you burn more calories than you consume. A pound of fat is equal to about 3,500 calories, and the average adult male burns about 2,000 calories a day without exercise. These means to lose a pound a week, one should consume a total of 1,500 calories or less in order to have a 500 calorie daily deficit.
This is the logic I followed, and I began to track the calories of every meal I prepared. I kept my diet to around 1,500 calories, with a bonus 250 calories burned through exercise. Using this method, I started losing about a kilo a week, but it was hard to tell since I was putting on muscle at the time as well. All I knew was that the fat began to burn when I started watching my caloric intake, and that's all I needed to see.