This is the truth, even if people don't like it so you're receiving downvotes for it. Weight gain or loss is calories in vs calories out. Nobody's body is so special that you're defying thermodynamics and creating mass that you didn't intake as food. And that's definitely not changed by sleep apnea.

That said, there is the point that calories ingested doesn't necessarily equal calories absorbed, and sleep apnea could indeed affect that. But if you're relying on that thin margin for the difference between staying at a healthy weight or not, that's a fragile state of affairs, and you could fix your diet more to be more comfortably on the right side of it.

(My own, unscientific, hypothesis: far too many people are indeed unknowingly relying on that. I think a ton of people cram in 3k calories a day while absorbing 2k because there's just too much mass for the body to process, and then when they do cut ingestion to 2k, that doesn't change absorption and that's why they don't lose weight. (Numbers here are approximate.) It's actually pretty amazing how little food the human body actually needs and how little mass 1500 calories is.)