What is the SNi mechanism of the reaction of moist silver oxide with a halide?
If you suspect that there is something different going on here, and I believe you are right.
My take, in the presence of lab light, $\ce{Ag2O}$ and $\ce{H2O}$ actually results, in the formation of the hydroxyl radical ($\ce{.OH}$) and the hydrogen atom radical ($\ce{.H}$) via the creation of a powerful photocatalyst couple $\ce{Ag2O-Ag}$ as outlined in this article: Ag2O as a New Visible‐Light Photocatalyst: Self‐Stability and High Photocatalytic Activity.
The photoelectric introduced electron hole $\ce{h+}$ and electron $\ce{e-}$ can act as follows in the present of water:
$\ce{H2O &lt;=&gt; H+ + OH-}$
$\ce{H+ + e- -&gt; .H}$
$\ce{OH- + h+ -&gt; .OH}$
The hydrogen atom radical is likely responsible for the extraction of the chlorine atom from the organic forming a product of $\ce{HCl}$.