He wants Pokemon from Pokemon Go that have not been transferred to another game then back to Home for him to buy.

Pokemon GO > Home = has Pokemon Go stamp (This is a one way street. Once transferred to Home, it cannot be transferred back into Pokemon Go)

Pokemon GO > Home > Switch game > Home = no more Pokemon Go stamp meaning it could be a hacked or modded Pokemon

correct. Just a way for me to verify the legitimacy of the pokemon

Not sure if you are still looking but I got shiny; Zekrom, Kyurem, Registeel, Suicune, Landorus still on pogo. Lmk