There are many reasons for updates from bug fixes, improved software to parameter mods. Each update will be for some or all of these. Yes your truck should accept latest updates. I know for fact that training of Toyota engineers with diagnostic tools is for want of a better word, crap but then again I can say with confidence that this is similar across ALL OEMs. No its not Mandatory to back up parameters BUT it is good practice. It's not something you will need to do often so if you call Toyota in and they mess it up at least you've put the ball squarely in their court.
I have supported engineers worldwide and I can say that even the best OEM techs with diagnostic tools are not being trained properly. Recently had a similar situation with another OEM who had their top tech working on a VNA truck. After 4 hours he concluded the main computer was bust and recommended replacing at a cost of €4500. I diagnosed the fault on the can bus and fixed for €50. No prizes for guessing who is looking after that customer now.