Copying the Wikibase Suite Deploy documentation on GitHub to Wikibase/Docker and then making it translatable could be useful for users of other languages.
Topic on Project:Village Pump
In theory you're right. In practice the devs unlikely to have the will or effort to maintain documentation in multiple places and if they prefer it on GitHub any local translations will just bitrot away.
Shouldn't this thread be on that work's talk page, Talk:Wikibase/Docker? Whatever the rest of us may think, it's their documentation and their decision on what should live where.