Thats the scam. They are acting both as broker and seller without transparently revealing the relationship.
It is like, you go to buy a house, the broker says the advertised price is 2 million, i recommend paying 3.2 million and then you realise the broker was the owner of the house.
And, even if they accepted the bid, I don't see the issue of not disclosing who owns it. Anyone who is selling something is 'suggesting' (setting) a price, so it wouldn't really matter if they disclosed they owned it or not because they are free to set the price. Why would you care if they owned it or not?
Do I understand this correctly? Maybe someone has a bridge they want to sell me
Their bidding mechanism is not how a retail transaction works, where either you buy or you don't, it is not binary.