Welcome to a huge problem here in WNY! It is a two fold problem, syndication and agents not placing sold homes under contract on the MLS. listings that appear on sites like this one are syndicated from the MLS, and there can be up to 72 hour delay in getti g the information. They also gather the information from multiple sources, that may or may not get the latest information about a property.
Inventory right now in som areas is so tight, that many agents keep listings active so they can get buyer calls on their properties. Agents are waiting until the home has passed home inspection to place it under contract, when they should be placing it the minute they have a signed contract.
My best suggestion to get the latest information on available houses is to work with an agent and use their website instead of these national sites. They have live up to date and accurate information.
Hope this helps you..