Jerome Av Line Station Rehabilitations

Ok, so they're rehabbing Kingsbridge Rd and Burnside Av right now. I looked at the service advisory and it said shuttle buses will connect the (4) with the (D). What is the point of that? It says a special shuttle bus will run between the Kingsbridge Rd (4) and (D) stations. What will that accomplish? And at Burnside, a shuttle bus will connect Mt Eden Av, 176 St, and Burnside Av (4) stations with the Tremont Av (D) station. Why? Why not just have a shuttle bus connecting these stations without the (D) station? Why even have shuttle buses at all, with the local bus routes (Bx28 and Bx32 among others) serving that purpose?

Oops, I said Kingsbridge Rd, when I actually meant Bedford Park Blvd.