Crashes caused by resource exhaustion are still software bugs in Firefox. At least on sane operating systems where memory isn't over-comitted.
He doesn't explain anything indeed but presumably that code is available somewhere.
We have long known that single bit errors in RAM are basically "normal" in terms of modern computers. Google did this research in 2009 to quantify the number of error events in commodity DRAM https://static.googleusercontent.com/media/research.google.c...
They found 25,000 to 70,000 errors per billion device hours per Mbit and more than 8% of DIMMs affected by errors per year.
At the time, they did not see an increase in this rate in "new" RAM technologies, which I think is DDR3 at that time. I wonder if there has been any change since then.
A few years ago, I changed from putting my computer to sleep every night, to shutting it down every night. I boot it fresh every day, and the improvements are dramatic. RAM errors will accumulate if you simply put your computer to sleep regularly.