It started at 5th gen with reshikrom I don't really care about it to be honest, if they do it for one pokemon let them do it for all the intractable and roamers
Out of curiousity, where did you read/find out that the legendaries of ORAS are checked? I've not seen anything about it either way in the datamines and such as of yet. I mean, I do expect Groudon/Kyogre/Rayquaza/Deoxys are checked, but... the trade ban on trading shiny Reshiram and Zekrom WAS lifted so I'm wondering if maybe the mirage legendaries aren't checked after all.