We can only hope!
Regarding the video I received PMs about this matter before. I'm rather annoyed about how this was done... (The comments in the video are really hilarious though...)
If you want to brag about distributing a "legit" looking Mystery Gift at least do it the right way. As @theSLAYER already mentioned, there are 2 options for distributable Mystery Gifts.
With the 1st one the received Mystery Gift won't be distributable and this means it will become legal in case you edited an official event, the received data will match the original Mystery Gift.
The 2nd however will always send distributable Mystery Gifts matching the edit, which means they're just as illegal as the edit.
You can see in the video that they decided to use option #2 as the received Mystery Gift has the "おくる" option.
By the way... there is actually a chance that some Gen 3 Mystery Gifts have been officially distributed this way.
It was at least the case with German Emerald Aurora Ticket and it has been reported here. I assume it was a leftover from debug but it could be that it was actually planned as an alternate disribution method. How many of those exist, we will never know...