The likely answer is the first thing I said then. If you scanned Eternal Flower Floette early on or have ever had one hacked into any gen 6 or 7 save file, it caused chaos on your Home account's Pokedex flags, causing a bunch of flags which shouldn't be checked to become checked. That's where all my Pikachu entries came from. It never was in the Home dex officially, but Home didn't have any error handling for people who had that entry through either the QR code pack, or through having hacked it.
Fair enough. It was a few years ago and I was doing a bunch of different things in an attempt to fill up the shiny dex by pretty much whatever means I could.
