In the shiny hunters thread: He doesn't. He calls them legit because they pass legal.exe's checks, which is known to not test for everything. It also doesn't tell you what it verified as. Suppose you start a new game and pick the name, ALAMOS. You hack your IDs to be the same as the event. Then, you teleport to Darkrai's island and SR. You get your shiny, then you hack it to be in the Cherish Ball and give it the correct Trainer Memo and ribbon. Hack detectors don't look at these kinds of things; they expect the user to check them himself. The hack detector will see this and think, "Oh, SR poke here. Pass." and return a pass, even though it's for the wrong reason.
Response:
Actually Legal.exe will tell you whether its a mystery gift pokemon (they can still be hacked to appear to be) and Color Me Evil does not trust legal.exe despite being more comprehensive than SHC.
So actually that one would not pass in either. ;) The checker that Color Me Evil uses only checks for, so called, trash bytes. If its caught from the in-game location it will not have the proper trash bytes.
But the trash bytes for mystery gift pokemon are extremely easy to figure out. All the person who hacked it needs to know is how to open a hex editor and know where the PID is located.
Also are only members allowed to post in the shiny hunters thread?