I got into a debate about that with a friend of mine. A nice argument, not a heated one. He is a fan of agile. I am not. He is developing chargers for lithium polymer batteries, and runs an agile embedded team. I tell homie that agile, modular, development only makes sense if you have realistic expectations of significant scope creep. I mean, seriously, your only job is to charge a damn battery, why bother with bullshit?
We drink about that argument often. My only job is to turn lights on and off, albeit with input from photocells and occupancy sensors, but really zero modularity is needed. Super straightforward. HC11 kinda straightforward.
I think you are right though, I got triggered and all hysteretic. 