I think that, as it does seem like the Bl 4 signing was "pushed" toward an early resolution, that it was because the experienced parties felt that STP was possibly going to go cold by the set later date (2/28). STP signs off on Bl 4 and they probably have no recourse on the rest of the blocks. But, maybe as some in Nigeria feared, STP bailed out at the last second anyway hoping for a bigger piece of the pie.
Just my speculation, I haven't been able to get anyone to answer a telephone call.