You really think that is a deterrent?!? LOL!!
Unfortunately, the assumption the information was on said Event Flags is wrong. You will notice that the link you provide makes no mention of the Dex-less Mythicals. No Mew, Celebii, nor Genesect. However, no shortage of players can confirm that a Pokémon Go mon produces an error in Home when trying to trade it to Sw/Sh were the same species is not mapped as caught. Non-Go mons are permitted to unlock data but Go mons are NOT permitted to unlock Dex data for you.
I assume the base Dex data is stored as an array. So, there has to be an array connected to or with the existing Dex data.