Agile tries to solve this differently.
First and foremost, it puts you into tight-knit communication with your team and the customers, so just ask if anyone remembers why it is like that.
If no one does, then Agile enables to basically fuck around and find out.
Which is to say, change it to how you think it’s supposed to be and see if anything breaks / anyone complains. If that happens, Agile allows you to react quickly, i.e. to change it back and quickly release a fixed version.
But yeah, as the others said, if your team feels like documents work better for them, then do Agile and documents. That’s why retrospectives are an integral part of Agile, because it’s not a perfect plan how to work together. You’ll know best what works in your context.
It’s certainly simpler than Forza et al, but there’s an open-source racing simulator, called Speed Dreams: https://www.speed-dreams.net/
If you watch the “Latest Release” video, there’s some engine sounds in that.
They seem to have a bunch of samples for how different car models’ engines sound: https://sourceforge.net/p/speed-dreams/code/HEAD/tree/tags/2.3.0/data/data/sound/
And then they modulate that in code, based on the car’s speed, gear, turbo etc.:
https://sourceforge.net/p/speed-dreams/code/HEAD/tree/tags/2.3.0/src/modules/sound/snddefault/CarSoundData.cpp#l171
They also do that for gear changes, tyre sounds, collisions and backfires.
From what I know about audio, I would expect AAA games to still use the same approach of recordings+modulations.
While it is possible to fully synthesize an engine sound, it doesn’t help you much with making it sound right in all different situations.