if it was flawless youde know because it would most likely be rng.
flawless means its ivs are flawless meaning 31 in every stat. there is a way to check a pokemons ivs by going into serebis main site here is the link.
but it is only accurate once a pokemon is raised to level 20 or higher. so if you had a pokemon lower than that level save your game raise it too 20 and then check it. reseting your game after. hope this helps.