In any real estate transaction, a contingency is a contingency whether it is written into the contract or not.
In this crazy market, buyers are trying to present the best possible offer even if it means hiding important considerations such as the contingency of selling of another home. Any agent that colludes with a buyer to hide any material fact is violating their ethical duty. For me, talking to the agent and lender is an easy way to flesh this out.
Good advice from the National Association of Realtors – Does a buyer have to disclose his contingency