At many companies (I want to say most), Redis is seen as an actual durable production database and operated that way, not just as a cache that can disappear at any time. It's not unreasonable for a new dev to assume this unless told otherwise.
That’s not been my experience.
Ultimately though, regardless of whether you’re experience is true for the wider industry or not, if you’re letting a junior dev who refuses to read product documentation the responsibility of architecting production systems, then your problem isn’t Redis.
Sure, but that is an internal documentation failure not a redis failure. It feels incredibly unfair to blame redis for that.