It is exclusivity. I've been involved in some of these contracts going all the way back to the Summer of 2004 and they absolutely involve exclusivity. If Safari or Firefox product managers added a new search access point and their business people tried to sell default placement for that new search access point, they'd violate their contract. That's exclusivity. Opera used to do that kind of thing, they had three different search defaults for three different access points in the 2000s but by 2010 Google was no longer allowing that in their contracts because exclusivity.