For SWSH, any grass encounters, overworld encounters, roaming encounters or fishing encounters, has a known PID IV relationship, that you cannot just hack randomly. (There are a few exceptions, which you can read in Anubis's gist linked below) Detection for that has been implemented into PKHeX. Legality report will show "Encounter Type PID mismatch". Data that has a correlation presently: EC-PID-IV-Height-Weight (all chain generated from one encounter seed)   While it's possible