That's not firmware, that just means channels have been added/removed and you need to (in effect) 'retune' your receiver to add/get rid of them.
As I say, given the system at work, even if there was one you're actually unlikely to check in the small window it's being broadcast anyway just by checking manually. Most of the better boxes (including Sony's IIRC) actually check on an schedule automatically.
You have to remember freeview receivers (and even more so DVRs) are basically computers. They have a CPU, RAM and an OS. Much like a computer that OS needs updating, either to fix bugs, add new features or because the freeview environment changes. Normally you'd have fairly frequent updates when the box is new, tailing off over time as it's replaced by newer models.
You'd expect so yes. I have heard stories of corrupted downloads though. I suspect though some receivers have been made for the minimal possible cost and that includes coding how firmware updates are applied.