The agent acts for the seller and this could be an arrangement between the seller and agent that all offers will be checked as financially viable. Who cares!!!! Show them your AIP and tell them to update you on your offer ASAP or by close of business. Why bother getting all worked up about? By the way an AIP agreement in principle ain’t really worth a lot as it does confirm your credit worthiness but until all info credit search, credit score, payslips or accounts for self employed, maybe 3 months statements, full ID, maybe proof of child benefit / tax credits, mortgage valuation etc etc you have not got an offer. So even with an AIP things still get declined.