I agree it will diminish the value of key numbers but I really disagree that a team is going to take a knee on the extra point attempt if they're up 9 with 30 seconds left. The defense can score 2 in college and you don't see people taking a knee.
I would say giving a team the ball down 9 would make them 250/1 to win as opposed to 500/1 if they were down 10. In addition, in the extremely rare case that the PAT was blocked and run back, recovering an onside, scoring a TD in 30 seconds, then winning in overtime would be around 100/1 by itself
These are all assuming both teams are equal