Everyone assumes the vegetables make it light. They do, but the vegetables were never the problem. Spinach, bean sprouts, carrot, zucchini and mushroom come to about 60 calories for 150g. The rice underneath is 310. So a bowl with the same toppings on 140g of rice instead of 210g drops to about 510 without you noticing much.
The sesame oil is the sneaky one. The kitchen drizzles about 5g on top and you probably add another 5g from the bottle on the table. Each teaspoon is 45 calories. The gochujang is another 45 for a full tablespoon, most of it sugar. Together the oil and the sauce can be 130 calories for something that takes up no space in the bowl.
Dolsot bibimbap is the higher version. The stone bowl is brushed with oil so the rice crisps, which adds 50 to 80 calories, and it usually comes with a raw egg yolk rather than a fried egg (about the same, 70). Yukhoe bibimbap with raw beef is similar in calories to the standard, since the beef replaces the fried egg rather than adding to it.