Earlier quoted context omitted.
Imo the key difference here is that they're owning the decision and not trying to paper over the fact that it is no longer OSI Open Source. The three year change is also a big deal in my mind. Would make me a lot more comfortable to adopt knowing it is absolutely guaranteed to become OSI Open Source later.
My point is that they are able to own the decision only because the public opinion has accepted it as a new reality. If CockroachDB was the first OSS database company to do this, they would have a much harder time explaining their rationale. MongoDB et al have paved the way for them.
Cockroach also have the benefit of hindsight to avoid some of the problems Mongo/Redis et al encountered.
Calling this a "Business Source Licence" avoids the terminology problems so many people complained about with Mongo's perhaps badly chosen "commons clause" rider on top of (and fundamentally changing) a well know open source license.
I think the rolling three year time limit is probably a smart reaction to some of the complaints people have about other companies attempts to tie down some of the rights while providing assurance that there's at least be an option open in the future no matter what happens to the company.
I wish them well with this.