273 Block Casting Recesses, did we find an answer?

There was a tread recently about 273 blocks with areas cast on the drivers side to clear power steering or manual steering boxes.
I can't find the tread anymore, but was there an answer about why they were cast that way?
I don't see 318 or 340 blocks having that feature.
I have a 65-69 cast block by casting number 2806030-3 that has the inverted "bumps".
Any thoughts?
2806130 65 69.JPG IMG_1767.JPG