I agree that it's a personal choice. And no, I don't think you're thinking about it too much. I think it's wise to consider the possibilities.
IMO, I'd have to 'side' with aclee. We're both CC. Our first two are Asian and it was important then---as it is now---to us, to adopt more than one child of a certain ethnicity. The first two are now grown and on their own. Several years ago I asked them if this made a difference by having a sib that was 'same-same'. They said at the time, that they didn't feel it did.
Still....in our area, this is important to us. Our three at home now are all full AA. We've updated our homestudy and have requested full AA again.
(I did laugh at the Noah's Ark comment!
Never thought of it this way; but, like I said, for us, it has always been important this way. )
Sincerely,
Linny