Gatorade gets its carbs from sucrose. So it’s 50/50 glucose and fructose. If you hit 90g of carbs an hour that way, you’re taking in too much fructose, which is generally associated with discomfort, flatulence, and feeling bloated.
On top of that, clearly whether it’s isotonic in the stomach (and the extent to which that does or does not impact gastric emptying) is not exactly the same as whether it’s isotonic in the small intestine, which seems to matter for blood uptake (of everything you are trying to put in… carbs, water, and electrolytes). Of course, the quantities of water and electrolytes that you are trying to replenish will depend on a person’s sweat rate, sweat sodium concentration, and conditions.