This is a weird and rather late question but it doesn't hurt to ask I suppose.
I don't remember when but I remember logging onto Pokemon Home on my switch and having a bunch of Pokedex entries I had never registered before. Specifically, it was a lot of Kanto Pokemon, but there are some others like the Unovan Monkeys that stand out as well. This likely happened when I used my brother's 3DS to shiny hunt Ultra Beasts in Ultra Sun and transfer them up to my Pokemon Home (I might only have stolen his cartridge but I do believe I still transferred using his 3DS before).
So is it possible that Pokedex data from my brother's Pokemon Bank transferred to my Home or did something completely different happen?