Agreed, the main benefits DCVS bought is the ability to work without a constant internet connection and efficient branching/merging.

For the rest most companies are using git in a way very similar to svn, but now Github/Gitlab/Bitkeeper whatever provides the role of a single authorative central server.

Your first sentence is hard to parse, but it seems like you are saying (1) DCVS has more efficient branching than git, and (2) implying git requires a constant internet connection. In which case, (1) is dubious -- got benchmarks? and (2) is simply incorrect.

Is DCVS not just a typo of DVCS, ie Distributed Version Control System, of which git is one?

correct