Be interesting how this contrasts with the cc65/ca65 tool suite, which is pretty complete I think in terms of assembling, linking, and libraries. (Discounting the actual C compiler part.)
What I liked best about it is the portability, the scoping, and the preprocessor, which I prefer in particular to how many other assemblers do macros, and that's why I ended up taking it over (though Andre still did a lot of the code in this release too). The linking is not something I personally use much but other people do, and the O65 binary object format it uses covers a lot of use cases.
Now, I don't think anyone would blink at constantly rebuilding 100K lines of assembly. It takes seconds on modern hardware. We even see that in the C world with large utilities shipped as a ".h" file.