I wouldn't call shifting all the boxes to get the detection working shady, but it certainly isn't ideal.
Well, it's an unannounced distribution, I'll give you that.
However, do note that all of HOME's mystery gifts so far have been unannounced:
Initial Login Pikachu, Kanto Starters, GTS Rotom, Wonder Box Eevee, First Challenge Pichu.
The National Dex Completion Magearna looks as official as the other ones I just named.
(Granted, the initial copy looks glitch/bugged, with impossible moves and 15 ribbons lol)