Having the IDs/PID locked is a way Nintendo officializes things, and can see if that special move they added to the event Arceus n00bhacker brought to the VGCs was (exactly identical to one) possible to obtain from this event.
Let me introduce you to Event Traders, who are 100% anal about what data the event comes with. They have their own "rarities" placed on lesser distributed mons, and if someone created a similar appearing hack based on public information, they could call out the imposter on it. Kinda like fiat money, of course you could fake it, but a n00bhacker can't create a flawless hack without the same printing plates / paper / blueprint.
Also of course there's no legal 31/31/31/31/31/31 Naive Heatran possible from gen4, nor is there a shiny Flawless Jirachi possible.
People are OCD and don't like hacks because they don't have access to them, or are just naturalists. RNGers don't like hackish acquisitions of things they can RNG because the hacker doesn't have the skills to do it without something else intruding and doing it for them. They don't have teh skillz teh RNGers have (that's why they think that)