Your thinking is correct.
Not sure if understand wym by “autodownloading”, but no, AFAIK, there’s no means of “auto downloading” ebooks via calibre, legal or otherwise.
There is a section “Get books” with a search function in (and links to) prominent stores if you’re looking to buy some the legal way, but it does not provide “auto-downloading”, which implies some sort of high seas methods.
As such, it does not resemble the -arr type solutions out there. In my experience, it is best suited for management rather than procurement.
I’m tortured by my reflection. Our sustenance craves alteration.