If the quarrel is about facts or law or both, the adjudicator investigates those and is bound to decide according to the contract, and not his whims or sympathies. The only reason to require A to pay B is when B has a contractual right. As for the ambush, these two adjudicators are conscious of the process having to be fair. They have found a way for the adjudicator to put pressure on the ambusher, although I would simply dismiss the ambusher's claim on the basis that parliament's intention wasn't to create an opportunity to mug the other bloke. This pair are realists.
Adjudication exposes shenanigans.
This is a winner of a book. The second book on the Construction Act is by Martin Wood. He is a solicitor at Greenwoods at Peterborough. I expect he is kicking himself a tad. Wood put the final touches to his hard work last December.