> Is there really a large difference between 0 and 1 when the average tenure of a software developer is 3 years or less at any given company?

Spot on. 1 might as well be zero. Totally unfair to the worker also, who now cannot take time off.

When I was an architect for startups between 2016-2020 doing mostly green field development using new to the company AWS technologies, I made damn sure that any knowledge was disseminated so I could both take a vacation without being interrupted and I could “put myself out of a job”.

I considered it a success when I realized a company doesn’t need me anymore and I can move on and talk about what I did at my next interview in STAR format.

Agree, and also, promotion is hard if you are too tied to a specific system. Diagonal cross-department promotion becomes especially hard if you are a single point of failure.

But a Bus Factor of 1 has always been considered high risk. Sometimes companies take the risk, but that's a different issue.

This is precisely why the term "Bus Factor" was invented: to point out when it's 1, because it's both high risk to the company and unfair to the dev that cannot go on vacation or extended time off.

A Bus Factor of 1 has always been construed as high risk; that's why the term exists after all. Companies sometimes mitigate it, sometimes not, but in general they are vaguely aware it's a risk.

A Bus Factor of 0, especially as an implicit goal, seems doubly worrisome! Now it's a goal rather than a warning sign.