The article says that BPI was developed by ESPN analysts and if you look at Lunardi's Bracketology, it has a tab for BPI not RPI.
Call it an educated guess!
I've looked through several of his articles and watched several videos and I've never seen him talk about BPI. In one chant, someone asked a question about RPI/BPI and he only talked about RPI. As I said, my guess is he has the BPI there because that's what ESPN tells him to do but I think he actually bases his predictions on RPI because that's what the committee uses.