Yes, I did make the example overly simplified because I just wanted to trigger an ah-ha! moment. The article was already running long without getting into a lot of what if situations. To address your concern, it's pretty easy to convert various types of columns into a common type and concatenate them together in a function that would also process the MD5 sum. If the resulting length exceeds the HASHBYTES function's input limit then this method isn't for you or you need to come up with a way to shorten them somehow. There's no reason why a extremely wide column couldn't be put into two or three checksums in the XREF table.

Obviously this isn't the perfect method for everyone but I think some people will find it useful.