It’s not an assumption, rather a fact, and as you note, it’s a matter of the definition of “official”; to clarify, the developers have not officially made the Caddy software available through any package managers at all. Any Caddy package you find, as of this writing, is unofficial, provided directly by distro maintainers or volunteers based on the Apache 2.0 license the source code comes under.
It is something they want to get around to eventually, though (this thread is relevant: Packaging Caddy - #127 by carlwgeorge).
As for the reason why I resist, that’s not a mystery either - the closing statement of my last reply to you succinctly outlines why I don’t see the benefit of run-time configuration worth the downside, but to re-summarize: the benefit is small, and the downside is large.
I would contend with this statement as well; the fact that binaries exist for distribution (even if they were officially provided and maintained) via popular package managers does not preclude, in the slightest, the ease with which one can retrieve a binary from anywhere else (including any other unofficial package).