GP’s comment should apply to most if not all systems with a few caveats / divergences.
FreeBSD certainly mentions and lists standard sections at the top of `man man`. OpenBSD mentions the concept of categories / sections early on, though it only lists the specific section when it comes around to documenting the corresponding filter.
GNU invented info(1), not man(1).
We can still observe that effect in the Android ecosystem which started out really bad and fragmented and slowly drifts into a more coherent whole, instead of the other way around.
Many saw what the UNIX war led to and tended to avoid similar situations. I too liked what the BSD homogenous distribution let to on a technical basis, but the GPL makes sense as long as business cases can be made fit.
This case put a severe pall on the attractiveness of BSDs as they were suddenly in legal jeopardy just at the outset of the UNIX wars and as they were coming into their own.
And at the same moment, a cleanroom unix arrived on the market, limited in many ways but safe.
The GPL was at best neutral for most users, as can be seen from its adoption (or lack thereof). However the GPL was nowhere near as problematic as “AT&T might get our OS declared illegal”.
Red Hat, Cygnus and the IBM service group took early big bets on Linux, which could not have happened on a product where vendors based their respective offerings on proprietary lock-ins. That drove adoption in banking and defense whose existing UNIX stacks looked increasingly old, which drove a huge industry shift that took the better part of a decade.
It used to be quite common to find people arguing that BSD was the more "business friendly" license, which is may be true in some specific ways but tends to miss the bigger picture. The adoption of a mainstream system under GPL license was important.
Then the situation was probably different in the web hosting business, in academia, and in other sectors where other factors dominate.
Edit: "free" in quotatio marks to not confuse with FreeBSD.
And outside the datacenter? Was the problem of an Open Common Desktop OS - for those people who are radically *not* system-agnostic - solved at the time?
What could have been the effects on the trends building the scenario until today and beyond, had Linux not appeared but keeping the rest of the chessboard intact?