I can believe that with other foods but with seeds, its true in my experience. I was getting a lot of wasted seed , so much so i would save it and give it to the wild birds outside. Waste because my birds would only eat the seeds they liked the most. Now ill only give them a little bit and they will eat just about every last seed, including the ones they wouldnt before. They still get the vegetables etc. at the same time. Its not like im starving them.
I've tried to wait out Ripley's pickiness for several years, and I know from experience that it doesn't matter if it's seeds, pellets, or fresh food, I can leave it as the only food option for a couple days and he will just stop eating if it's not something he's interested in.
He also will just randomly stop eating some foods; most recently he stopped eating Harrison's. I left only Harrison's in his cage for 3 days and he didn't eat a single piece. He did have veggies available because I'm not a monster, but as soon as I put Zupreem back in his bowl, he ate with gusto.
In the past he has physically lost weight while I tried to get him to eat new foods, so I definitely don't think it's an option for every bird.
Birds are naturally neophobic, and if they don't recognize something as food, it's normal for them not to eat it, and some unfortunately will die because they don't realize food is available.