While this is of course technically true and stated outright in many "fine print" locations, CO has a habit if making changes for one reason or another and then not being up-front with the customer as to why the change was made, often relying on obfuscation and double-speak to brush off a customer with a legitimate complaint. Should craz have lost his seat assignment? Almost certainly not. The problem is that very few of the reasons for which CO might have done this are reasonable to a customer and CO doesn't want to explain it.

I had a similar situation flying with my wife EWR-ATL. I split the PNR after getting both of us into exit row seats so that I had a chance at the upgrade. Come to find out that my wife's 14F has been reassigned to 10F. When pressed for an explanation I had to go through four different people before the agent in the PC actually admitted to me what had happened - a pair traveling together demanded seats together and moved my wife to accommodate them. Even worse is that the agent in question put a minor in an exit row by doing so. And when I asked to have my wife put back in that seat I got the "we don't move people out of seats on a whim so we can't do that for her" yet they had literally just done it hours earlier to displace her in the first place.

Maybe craz got FAM'd. Maybe it was CO doing a favor for someone else at his expense. Either way, CO will never own up to the fact that they did a disservice to a customer, whether it is within their rights to do so or not.