Based on my experience with my Motorola modems, Comcast replaces the shipped firmware with a compatibe version of its own, even when the shipped firmware is newer. I would think this same practice takes place with other brands as well like Netgear. I also would think that any changes would be tested internaly every step of the way well before it would be released into the public production network.
I also would think that any changes would be tested internaly every step of the way well before it would be released into the public production network.
If you put 10 engineers in a room, and told them "Make it PERFECT" we'd still be on sneakernet.
I'm sure they are thoroughly tested (to death if needed, but some minor idiosyncrasies* must be allowed to exist) but some effects/defects don't show up until stress tested** which is the point of the limit rollout area wise, and system wise***
*Brandcentric "FEATURES" ** exposed to the billions (really!) of possible hardware/software/equipment/usage combinations possible when big iron touches small systems. ( I think will call it "Internet") *** I believe they are still in the ~~direct connect to a limited group of modems phase (this modem was known to be noncompliant, but not known to be incompatible)