It's a good idea to specialize planets. Yes, I do it too.
OTOH taking a planet with the same buildings on 80% or more of the tiles appears a little boring and makes me wonder how "realistic" that is. Or, since "realism" is always debatable in a game, maybe call it plausibility?
At least, if specializing planets has clear pros - shouldn't there be a downside to it as well (or is there already?). Or some other benefit for more diverse planets?