Hello!
That helped a lot! I am now understanding how this works better.
With that said, as you can see in the first image, that is from Maya LT. You can see the UV's are stretched to the other tile.
When you try to load that into Substance Painter, you will get an error that your UV's are crossing over tiles. Check.
In 3DC, I have no way of knowing ( as far as I'm aware of ) that the UV's are crossing over tiles. Is this a function that I just haven't turned on for the UV Preview looks correct.
Thanks!