[nostrademons]

I don't want to get into the specifics of the build system since it's proprietary, but there's a non-trivial startup cost for it. It's optimized for being able to compile really huge projects in a tractable amount of time, not being able to recompile individual files in the shortest possible amount of time. The latter will execute quickly enough (yes, it only recompiles what you've changed), but the startup time is still annoying enough to want to batch up edits.