Ah, you're right. Now thinking back, I think it was how Homebrew reuse system libraries that make it a better experience than MacPorts at the time since it could cut over half of the building time (it prevent the situation where `port install sl` ended up having to build the entire gcc toolchain). This was actually why "reuse system library" were such a big deal back then. Bottle come much later than that.
Homebrew not only installed from source for a long time, when they implemented installing prebuilt binaries, they half-assed the dependency resolution of it, so the binary version of a package would always end up requiring the binary version of the first of any alternate dependencies (ie if A requires B or C, binary pkg A will always require binary package B, and won’t accept C).