Popi Act (to support not making an offer)

Just had a buyer from we buy cars inspecting my car to make an offer. Everything went well did his inspection and took it for a test drive. Once back from his test drive he told me after taking down all my personal information and pictures of my car that he require a proof of purchase for the car this is before he will be able to make a final offer. I then drove home and found the receipt of the agreement which is signed between me and the previous owner with all the relevant details on it. He then told me that the document supply is not a certified proof of payment. I then asked him if he could supply me an example of a certified proof of payment he told me he is unable due to the popi act (really the popi act) you can Google a template and just show me an example of a certified proof of payment. He then asked me to get a report from vw to make sure my airbags are intact. Please we buy cars don't waste peoples time if you not making an offer or not interested please be transparent and tell people that instead of having them running around trying to pull hair from a frog.