Where does that support the claim that
Debian would oppose people working on
sysvinit support?
In the body of the other[2] email where 'Option 2 "Support for other init systems is recommended, but not mandatory"' was selected by the Debian community. Once this path was chosen, while it theoretically isn't opposition, in practice it was only a matter of time before non-systemd init systems would become increasingly difficult to use in a systemd-leaning distribution (sysvinit or otherwise).
As Manfred Eigen said:
In theory, there is no difference
between theory and practice. But,
in practice, there is.
As Manfred Eigen said:
(source: https://www.brainyquote.com/quotes/quotes/m/manfredeig211444...)