A week is just enough time to get a cursory understanding of the product and tooling and fix a newbie bug.
If it's a tiny startup on mostly greenfield stuff then sure, but that's also not a reasonable proxy for the rest of the industry.
After Google I joined a startup where I built two new products from scratch, including hiring most of the team myself. On boarding time was about a week and that included learning a new programming language from scratch (Kotlin, which is in fairness, easy to learn). This remained true true even after several years where the codebase had become quite large. On-boarding time never really changed for programmers of equivalent skill.
Ramp-up time in most normal businesses and most normal codebases is measured in weeks, not six months.