Yeah the "wait an hour" thing is such a lie lol. My mom used to enforce that rule so hard when I was a kid. I remember sitting on the side of the pool just watching everyone else have fun. It's crazy how many people still believe it. I looked it up once and there's zero science behind it, just an old wives' tale. Feels good to finally dunk on that myth.
Tell your mom she can relax now, the pool police have cleared the charges. Honestly, the only real rule is don't jump in right after a huge, heavy meal because you'll just feel sluggish and gross, not because you'll drown. I let my kids go in whenever, just as long as they're not complaining about a stomach ache from eating too fast. Common sense beats an old timer's tale every time.