Data verification for Time Machine?

What sort of verification? File bits are not used for verification of data. Data verification is generally performed in some other manner such as hash codes or re-read after write, packet data headers, etc. A filename bit can be set to indicate if a file has been archived, if it's readable, writeable, deletable, executable, and the like.

Well, the operating system normally does packet verification on its own during all disk read/write operations. This typically involves creating a hash code that can be used to verify that the data in the packet is correct. I'd be surprised if Chronosync's advertising is simply reporting what the OS does.

In this respect, TM is verifying that the data written to the backup drive is the same as the data read from drive backed up. However, it can't verify if the data itself is correct. In other words if a file is corrupted on your drive, then the backup will consist of the same corrupted file.

You'll find that simply copying a file in OS X involves comparing the copy to the original bit by bit. The hash code is a code embedded in the packets written so that when the packet is retrieved at some later time the hash code is used to verify that the data being read from the copy is the same data that was written. The hash codes are unique so any defect in the copy from what was originally written will cause it to return a different code indicating a problem with the data in that packet. I fail to see how that is any different from what Chronosync is stating in their marketing information. Any piece of software could opt to suspend the use of normal data verification in order to make for faster file transfers in lieu of more reliable file transfers.

That said Chronosync is a good product that is a reasonable substitute for Time Machine. I certainly have nothing bad to say about it.