I thought it was about ECUs, automotive systems, and that other sort of engine. The title is equally suitable.
With regards to debugging software, I think being able to do so effectively even without source is an important and rather rare skill. And sometimes, even with the source, the compiler can introduce its own issues. Being able to read Asm and follow along with what the CPU is actually doing is exceptionally useful, especially when working with lower-level languages like C/C++. One of my friends has a saying along the lines of "if you can read Asm, software has no barriers to understanding."
There is "reading asm" and there is "debugging millions LOC compiled with an optimizing compiler". The later is possible but the time requirements would be just impractical for game development. Even having the source without the ability to modify is almost useless.
If he confused the definition of "engine," he's likely coming from the auto world, where things are (_mostly_, not everyone drives $100k Elon Musk mobiles) still microcontrollers with kilobytes of flash and RtOSes. There, it's still entirely possible to debug execution interleavings and the like by just staring at the ASM.
My old car, a 2002 BMW 325i, fits that description with a 25 MHz 16 bit Infineon C167 processor and 512kb of flash in its Siemens MS43 ECU. That's properly a microcontroller in my mind.
My new car, a 2015 Ford Fiesta ST, has a 133MHz 32 bit Infineon TriCore processor and 4MB of flash in its Bosch MED17 ECU. That's more than many PCs had until the late 90s, so while it's definitely running a RTOS I have trouble calling it a microcontroller.
That's not even a new ECU either, a friend's '09 VW GTI had basically the same unit. Anything with direct injection almost definitely has a 32 bit ECU, especially if a turbo is involved. I'd imagine a higher end car these days has something more potent (or just doubles them up, like BMW used to do on V12s).
It does make it much easier to report bugs if you have an idea of what's actually wrong (sometimes it's something rather trivial), and I have worked on a few projects where dynamically patching binaries was involved.
In Windows, there isn't really any other ways around something that MS decides is "won't fix", or just ignores you completely.
With regards to debugging software, I think being able to do so effectively even without source is an important and rather rare skill. And sometimes, even with the source, the compiler can introduce its own issues. Being able to read Asm and follow along with what the CPU is actually doing is exceptionally useful, especially when working with lower-level languages like C/C++. One of my friends has a saying along the lines of "if you can read Asm, software has no barriers to understanding."