I think this analysis is flawed. With the given constraints, each side knows they will have in total 520 +-70 hcp in a 26 deal set. If the NS average is 22.5 after 20 deals, they have had 450 hcp. Thus, they know with certainty that they will have 70 +-70 hcp, i.e. between 0 and 140 hcp, in the remaining 6 deals. They know, for example, that they cannot have the points for game on all remaining deals. That is knowing a lot compared to random deals. And of course, the situation could become more extreme closer to the last deal. Similarly, EW know they will have between 100 and 240 hcp in the remaining 6 deals. This means, for example, that balancing and competing for the part score will be pretty risk-free. EW know they will have some values and will not be unlucky in terms of hcp.