Yup, the voice installer is flagged for the PW2/KV/KT2/PW3. It's basically only missing the Oasis (in which case, KindleTool is your friend, either to get at the files, or to repack it for the Oasis).
(It does a platform check only, so it matches all Wario devices. Since the Oasis is based on a newer platform, Duet, and this specific variant of the package format doesn't support flagging multiple platforms, not flagging the Oasis is currently a technical limitation of the particular variant of the package format they decided to use).
But as was mentioned, it's nothing but a voice folder dropped in the USB root, so you really, really don't need the two layers of indirection that update package introduces to do that, but, hey

.