"It was a response to White's choice of a Catalan-type opening."
The response could have been prep. I am not saying he was going to play it from move one. I am saying that he had block of moves he knew about. Block 1 (including Bb7) and Block 2 (A bishop move along c8-h3 diagonal).
So I am asking about the choice to go right to Bb8 or left to c8-h3 diagonal. Again, Bd7 to Bc6 doesn't seem to come up as often, so is the choice to play block 2 a wiser choice?
As I said above, the Bc8-d7-c6 maneuver is BOOK in that specific position, played thousands of times. It's the most popular choice in that particular position, and has been for years now.
But in a generic position, either "Block 1" or "Block 2" would be much more common.
The choice between those two (develop on b7 or develop on the c8-h3 diagonal) depends on the position. There is no way to claim that one will be uniformly better than the other.
"There is no way to claim that one will be uniformly better than the other."
Ok, let's pose the question another way. People often say to study KID later on. If you were to teach a low level club player how to play as black, would you recommend getting the LSB or leave it be like in this game.
That game is again dominated by specific considerations, so it's not really suitable as a general example.
Black developed his Bishop c8-g4-e2-d3 because it was a very "bad" Bishop (look at all those Pawns on light squares!) and by entrenching it on d3 he could more-or-less force White to trade off his "good" g2-Bishop for it.
Typically as Black in the King's Indian Defense (an opening that I do in fact play with Black) I develop my c8-Bishop to a relatively modest square and bide my time with it. I might even leave it on c8 for most of the opening.
I should note that I'm not a big fan of "cosmetic" development... of moving pieces off their starting squares simply because "they look better" on a new square.
In the King's Indian Defense, the Black c8-Bishop can often play an important role without moving from its original square.
Example: Korchnoi vs Fischer, Herceg Novi 1970
I seriously doubt that Wei Yi decided in prep that he would play Bd7-c6 REGARDLESS of White's set-up. It was a response to White's choice of a Catalan-type opening.
He might have prepped it specifically for a Catalan, yes. It's the book move in that position, played thousands of times. Rare in other positions, though.
The Bd7-c6 maneuver is rare for a reason: because it takes time, blocks the c7-Pawn, pre-empts the c6 square from the b8-Knight, and leaves the Bishop more exposed to exchange (eg: by Ne5).
It is only good in certain concrete positions... such as this one, where White's pressure from the g2-Bishop makes b7-b6 impractical.