There are actually only a couple of items where a contract can be voided by the seller. There are plenty of contingencies where the buyer can void, however, a seller has about two paths to cancel.
Death is not one of them! Believe it or not most Contracts state that in case of the death of the Seller the heirs will continue to sell the property.
If the seller is wanting to find a house to move into before they complete the sale of their current property, and they cannot donation a certain amount of time, then yes, they could void the contract based on a home of choice clause.
Another area where the seller could cancel would be if there’s a third-party that is required to approve the sale.
Usually, this might be a short sale situation or where there are multiple sellers that must approve and if there’s no agreement then the responsible party can then cancel the contract.
Otherwise, once sellers agree to sell their house, they’re generally on the dime to make it to closing.
Have you had a situation where the seller wanted to cancel your offer??? How did it work out?