Yes, this method is what would or should be like the old SBF days, the file and process a VZW store will/would use to restore a phone to dead stock, no mods of any kind. It is also possible to use a method like JK posted, but with the various states of kernels, mods, webtop hacks etc. that folks are on, you will usually find some folks in every one of these threads that cannot seem to get it to work correctly. Or they have a modded and tweaked configuration that has not been tested for that particular process.
It is not to say that this process is or would be 100% for everyone, but it is the last resort route, and the process is one which everyone who mods their phone should be able to use. Especially with our locked boot loader. If you use this process, you will gain the ability to recover from any situation. Assuming it works. I had thought that one of these threads would have had someone flash and report by now, I hope that does happen soon.
Craig
edit: Forgot, Willboy, modding it will not happen. These FXZ files are moto propriatary, as is RSD Lite. The best hope is that we have one of these that gets leaked by a moto/VZW employee for each OTA version we get for the phone. If you are talking about going from 901 to the released official ota 893, this could work. If you are talking about going to 901 then these type of files are only acquired after an official OTA has been released, and someone at moto/vzw leaks the file to someone. I do not recall a leaked fxz/sbf file ever coming out at the point of OTA launch, only some number of weeks after, when moto/vzw decides the stores or employees need a way to flash a borked phone.