It's not that common though. I think breakthrough for alpha was non existent. Delta a bit higher but also nil w/booster, omicron, yeah that shit's everywhere.Vaccinated people getting covid is quite common.Getting covid twice is not.
Granted, alpha was already on it's way out when the vaxxes were released so I can see some delta instances getting mixed up w/alpha. I didn't even know we were tracking variants pre-delta to make that determination ( I suspect you inferred from timing).