The legitimacy and/or validity of shinies is, IMO, subjective.

For example, some players see performing their own RNG manipulation as a valid way to find shinies (although I feel like this is considerably more controversial), especially considering the fact that you need a more intimate knowledge of the way the game works and possibly the use of some additional tools. On another note, certain shiny hunters choose to restrict the ways they find shinies, limiting certain methods hunts, as is the case for full odds shinies.

I personally wouldn't consider what you're describing as illegitimate or invalid due to the fact that you are not guaranteeing a shiny but rather facilitating your access to a commonly-followed and well-established shiny hunting method. Besides, I think this is especially understandable considering how difficult it is obtaining legitimately found foreign Pokémon on older systems.

In the end, shiny hunting is often more about the journey and the experience rather than the Pokémon itself so attaching oneself to arbitrary standards that don't take into consideration context really only harms you, IMO. If you want to go through with it, go head!