If a seller is making warranties that they know to be untrue or conditional (eg possibly untrue), they will need to disclose this to the buyer in a disclosure letter. This helps prevent any claims for breach of warranty, as in delivering the disclosure letter the seller discloses against the warranty and makes the buyer aware of the facts before the Agreement that contains the warranty is executed.
From the buyer's perspective, disclosure letters help them to collect information from the seller relating to the warranties. This information may not have been provided during due diligence. It's important for the buyer to obtain effective disclosure, as this will allow them to negotiate and adjust the purchase price of the assets before completion, or even restructure the sale as a share sale, if appropriate (eg if a disclosure letter informs them about a significant upcoming legal claim).
Ask a lawyer if you need help creating a disclosure letter.